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So as the title states i have a 1989 C1500 Scottsdale with a 350 TBI TH700r4. I belive it has the stock gears though i was told it has 3.73. Anyhow there are a couple different things.
First it has to crank 4-5 times before it will fire on a cold start, Hot start it will fire up with 1/2 to a full crank. I cant find any vacuume leaks. Starter was tested and is okay. All grounds are fine(dunno if that would even affect this). I have checked pretty much everything i can think to check except the TPS.

Second of all when going down the road when i give it throttle to speed up it kinda bogs down, i have to pretty much stand on it so it will rev up( come out of OD) and gain speed. It doesnt matter if its in OD though. Does the same in D, i cant gain speed unless i make it downshift otherwise it boggs. It idles fine. Runs a little rich i can smell the gas in the exhaust but i also dont have a Cat.

Here is a Ful;l list of everything that has been replaced in the last 6 months. Fuel pump, fuel filter,(oil n filter), pcv, plugs, wires,Dist(complete with cap and rotor), Ignition coil(ACDelco), Rebuilt the TBI yesterday, New injectors, CTS, MAP sensor, EGR valve, reset the timing with a light( just put it at stock 0* BTDC). I cleaned but didnt replace the IAC when i rebuilt the TBI it was pretty dirty but seems to work properly.

I cant for the life of me figure out what is wrong. It idles perfect great throttle response. Just boggs when doing about 40-60 and i try to give it gas like to go up a hill. I have checked everything 100 times to no avail. I do get a soft code from time to time after driving for a while but since its a soft code and i dont have an OBD1 scanner i dont know what code it is throwing ( i know no help there):nono: The only parts i havnt replaced or thought to really check until recently are the O2 which is a $15 fix and the TPS which run about $55 here. i dont know if wither would cause the problems i am having.
**Note** i have an adjustable fuel pressure regulator and when i redont the TBI i raised it 2 full turns. Seemed to help a little on the low end but not where i need it. Also i do not have a Tach or Pressure gauge. Not that it matters one way or the other but it will still burn the tires off, but only if i hold the brake(doesnt like to "peel out"). Sorry for the Long post.
 

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Discussion Starter #2
So i was wondering if the accelerataion issue could be Valve related? Maybe something in the heads? Injectors spray perfect at all rpm ranges. IAC and TPS are good i have tested them. Maybe a Bad CPM/Prom? Just seems like bad throttle response. Throttle cable is good and tight though. Butterflies are spotless. Esp. now after the rebuild.) Oil looks great due for a change in about 700 miles though. Trans fluid looks good and doesnt smell burnt. I doubt changing the rear diff fluid would make a difference. I dont have a way of checking fuel pressure though but seeing as how i just replaced the pump and sending unit along with the filter and pressure regulator with no leaks i dont think it would be the issue.:smash:
 

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When it is cold, after setting all night, remove the air cleaner.Look at the throttle body , get a good light on it so you can watch for fuel spray.
Have a buddy, or the wife, crank it to see if it is spraying fuel or not at first start.


If not, then check for injector pulse.(You can usually hear them clicking on and off) or check with a NOID light.


If the pulse is there, then you need to verify that the fuel system is powering up, and then subsequently making fuel pressure.


It kinda sounds like the fuel system is losing its prime overnight. Even though the fuel pump is new, it could have a bad check valve and not hold pressure due to this.
Also the regulator could be leaking pressure off overnight and allowing the fuel lines to empty, leaving only vapor(AIR), which would necessitate fuel in the entire line from the tank to the engine Hence the long crank/hard start first start of the day.
You will need to get a fuel pressure gauge with a range of 0-15 PSI to accurately check fuel pressure on a TBI system as the normal pressure is around 13PSI. A small variation of just a 1 Psi or 2Psi will not show accurately on a fuel pressure gauge with a higher pressure reading as with a 100 PSI gauge for example, can have a tolerance (innacuray) of several Psi so.....


I have, in the past, cycled the key on then off 5 or 6 ttimes in a row (not to the start position) cycling the ECMs 2 second pulse for the fuel pump to prime the system after which the car started almost as normal. It proved out the fuel system prime theory and gave me some direction to go with my diagnostic routine.
So you could try that as well after checking for lack of fuel spray at the TBI

It is possible that the ECM (or computer) is not cycling the fuel pump relay when first turning the key on, which would make a hard start first thing as well.So listen for the fuel pump relay when first turning the key on. AND , just because a relay clicks on and off DOESNT mean it is powering up the pump circuit so you may need to verify that as well.


What was the "soft" code you were reffering to?


Here is how to get codes without a scanner:


OBD Diagnostics


The section you want to use is the "paper clip method" section.
When retrieving codes payclose attention to the blinks when it is broadcasting them. Getting out of sequence with the flash codes is a common mistake and muddies the "Diagnostic Waters" LOL


I know this is a lot of info thrown at you all at once, but just read through it , take it one step at a time. Write down the results on a checklist (paper) so you have an active record of what is going on
 

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Recap:

1 check TBI for fuel spray
2 check fuel pump relay action
3 verify fuel pump relay is powering up the circuit
4 hook up fuel pressure gauge verify when cold (after setting overnight) that pressure comes up as fast as required and is also to spec when running
5 Monitor pressure when driving at RPM range that driveability issue occurs
6 perform code retrieval as outlined in the link Paper clip method section


You are lucky. A simple TBI EFI, paper clip diagnostics .....;)


Some of the OBDII Can systems can be a challenge LOL


Keep us posted......... LA
 

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Discussion Starter #5
I am actually getting ready to pull the TBI back off, i heard you can test the injectors with a 12v battery and listen for a click. I know mine work so not sure that would do much. Now if this helps, i forgot to mention the truck was completely re-wired. The injectors and everything had a new harness put on. Maybe a ground is in a bad place uner the truck that i am not aware of? ill check a wiring diagram. I will let you know what my testing provides. Ill do the Scanner trick first.
 

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Discussion Starter #6
Okay so it is showing 12 (which i cant find anything on) 32 (just replaced EGR maybe a bad solenoid?) and 22 which i can re test the TPS.
 

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12 will be no distributor reference pulse (because dizzy aint turning so...)
It (code 12 ) is used as well to determine the start of self test readout
32 is EGR system. Shop manual says to fix any other codes stored FIRST.
So....the code 22 TPS.......the fact it has a TPS code would be enough for me to change it.
Be sure the wiring up to the TPS isn't melted inside where it is taped first.
Without a TPS value, or if the value is intermittent, it could surely cause driveability issues.
If the code 22 is fixed and you still have an EGR code , then proceed to repair the 32.
 

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Discussion Starter #8
Grabbed a TPS from a junl yard 3 minutes down the roads from me and it works. Also when i took the TB off i took the egr off and there wasnt any carbon deposits and it was seating all the way. Holds vacuum. I hooked everything back up, Drove it about 30 miles (round trip) changed my oil. Didnt have an issue. I had reset the battery though. Had the neg off for about 45 minutes. If the SES light comes back on ill let you know. If it does it will do it on my way to work in the morning. Ill let you know. But for now that seemed to have done the trick. Also replaced the O rings on my fuel line and return line. Hopefully thats where it was bleeding off. Will find out in the morning when i go to start it for work. It would help knowing the miles on my motor, Body has 277k but motor isnt original. No clue about the miles on it. Also would a tranny flush n filter Blow my tranny like everyone says. I have never done it to be on the safe side. I believe its the original Trans.
 

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Drop the trans pan and change the filter. Refill. Then do a closed loop fluid exchange.
Don't use any so called "flush" chemicals. ATF is high detergent fluid.
Flush chemicals ....who Knows?....:)
 

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I'm with LATECH on this one. I think your newer fuel pump is the culprit. Or is it possible that the TBI rebuild kit came with the wrong pressure regulator? You gotta be careful because they changed fuel pressure around that time.
 

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Discussion Starter #11
Well, Hard start is still there, cant find any leaks. Will i have to replace the entire pump/sending unit or can i just replace the pump? And i got the complete overhaul kit so i hope its not the wrong regulator. It was doing thjis before i replaced it. SES light hasnt came back on yet though so thats a plus, mainly just the hard start now.
 

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So as the title states i have a 1989 C1500 Scottsdale with a 350 TBI TH700r4. I belive it has the stock gears though i was told it has 3.73. Anyhow there are a couple different things.
First it has to crank 4-5 times before it will fire on a cold start, Hot start it will fire up with 1/2 to a full crank. I cant find any vacuume leaks. Starter was tested and is okay. All grounds are fine(dunno if that would even affect this). I have checked pretty much everything i can think to check except the TPS.

Second of all when going down the road when i give it throttle to speed up it kinda bogs down, i have to pretty much stand on it so it will rev up( come out of OD) and gain speed. It doesnt matter if its in OD though. Does the same in D, i cant gain speed unless i make it downshift otherwise it boggs. It idles fine. Runs a little rich i can smell the gas in the exhaust but i also dont have a Cat.

Here is a Ful;l list of everything that has been replaced in the last 6 months. Fuel pump, fuel filter,(oil n filter), pcv, plugs, wires,Dist(complete with cap and rotor), Ignition coil(ACDelco), Rebuilt the TBI yesterday, New injectors, CTS, MAP sensor, EGR valve, reset the timing with a light( just put it at stock 0* BTDC). I cleaned but didnt replace the IAC when i rebuilt the TBI it was pretty dirty but seems to work properly.

I cant for the life of me figure out what is wrong. It idles perfect great throttle response. Just boggs when doing about 40-60 and i try to give it gas like to go up a hill. I have checked everything 100 times to no avail. I do get a soft code from time to time after driving for a while but since its a soft code and i dont have an OBD1 scanner i dont know what code it is throwing ( i know no help there):nono: The only parts i havnt replaced or thought to really check until recently are the O2 which is a $15 fix and the TPS which run about $55 here. i dont know if wither would cause the problems i am having.
**Note** i have an adjustable fuel pressure regulator and when i redont the TBI i raised it 2 full turns. Seemed to help a little on the low end but not where i need it. Also i do not have a Tach or Pressure gauge. Not that it matters one way or the other but it will still burn the tires off, but only if i hold the brake(doesnt like to "peel out"). Sorry for the Long post.
The startup doesn't sound that unusual for a cold start but begs the question how cold? TBI suffers the same problems in the plenum and ports as do carbureted engines but it has even less heat as the intake is water cooled or heated in this case. What looks like an exhaust cross over isn't the driver side goes nowhere the passenger side feeds the EGR so the intake doesn't get hot till the coolant does. The manifold still carbons up to a point where it doesn't supply enough exhaust to keep the EGR functional in terms of the amount of exhaust gasses available to the intake, this will set code 32. Additionally, cruise RPMs is where EGR is functioning, without enough exhaust gas the mixture falls lean because the intake is filling that space with air. If there is enough space in the computer logic and the O2 sensor is good it will add fuel whether enough to correct the mixture I don't know. Code 12 is the computer telling you it's alive and well. Code 22 could be a mixture discrepancy between the throttle position and the O2 data. OBD-I isn’t too discrete; the diagnostics require the tester to have an understanding of systems logical relationships rather than having the ability of the diagnostics to point and grunt "go here, fix problem".

A 1989 brings pictures of high mileage; high mileage brings pictures of a dying timing set. Chain stretch causes the cam to lag the crank which also takes the distributor with it. In the case of TBI the computer adjusts the timing which if this was a carb you'd be doing it and might become aware that constant distributor adjustment was an indicator that something was wearing out, in this case that's transparent till it gets beyond what the computer can patch up. Idle could be right but as engine RPMs pick up the computer may run out of authority to fix the problem. From that point on the spark would appear to be late this would clip further power increase is some amount if not total. With the brown/black wire disconnected so the computer isn’t playing with the timing run the RPMs up about 3000 then slam the throttle closed, with a timing light on the marks, if they move off and around the zero mark, you know the cam ain’t tracking the crank or the distributor is out to lunch in terms of a worn gear and/or bearings.


Bogie
 

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Well, Hard start is still there, cant find any leaks. Will i have to replace the entire pump/sending unit or can i just replace the pump? And i got the complete overhaul kit so i hope its not the wrong regulator. It was doing thjis before i replaced it. SES light hasnt came back on yet though so thats a plus, mainly just the hard start now.
Several years ago I had an 89 that came in to be checked out for a very similar problem.
Took some looking to find it, but....and I am not saying yours will be the same but....I found the wire to the pickup coil in the distributor were corroded almost in two. I replaced it and it must have been the problem because it fixed it.
Funny thing is it still had spark but wouldn't spray the injectors.
Must have been sending a signal that was too weak to Feed the Ignition and the ECM
That being said, the TBI system is very good at startup especially cold as it sprays the fuel, promoting atomization, unlike a carb that requires the fuel be siphoned through small orifices in the carb before it even atomizes .
A TBI is a very dependable cold starting system even in the face of -25 degrees and better.
I wouldn't worry about any timing chain problems at this point as it is a dual row chain and not the morse silent type. The dual row is used in roller cam engines because it is less prone to allow timing fluctuations due to design alone.
I would try spraying down the throttle and then try to start it first thing in the morning to see what you get.If it starts with a spray then fuel is lacking for some reason.
It would really benefit the diagnostic routine if you had a pressure gauge on the system to verify cold startup pressure or lack of, or slow to build pressure.
Better to diagnose than to throw parts at it.


One other option for cold startup fuel starvation (a presumptive test) would be to turn the key on don't crank, wait 2 seconds. This cycles the fuel pump by using the ECM 2 second pulse that turns the fuel pump on to prime the system. You can cycle the key 4-5 times. Be sure to listen to be sure the fuel pump relay is indeed cycling. Then after that see if you get a decent cold startup.
If that seems to help the startup situation the it is likely the pump check valve is not holding or the line in the tank between the pump and the fuel outlet line is leaking.


At any rate you really need to nail down if your cold start problem is fuel related.
Be sure the fuel pump relay will cycle and that it is powering the circuit
Get a fuel gauge and hook it up.
Stop guessing at it.
 

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Discussion Starter #14
Well, Hard start is still there, cant find any leaks. Will i have to replace the entire pump/sending unit or can i just replace the pump? And i got the complete overhaul kit so i hope its not the wrong regulator. It was doing thjis before i replaced it. SES light hasnt came back on yet though so thats a plus, mainly just the hard start now.
Several years ago I had an 89 that came in to be checked out for a very similar problem.
Took some looking to find it, but....and I am not saying yours will be the same but....I found the wire to the pickup coil in the distributor were corroded almost in two. I replaced it and it must have been the problem because it fixed it.
Funny thing is it still had spark but wouldn't spray the injectors.
Must have been sending a signal that was too weak to Feed the Ignition and the ECM
That being said, the TBI system is very good at startup especially cold as it sprays the fuel, promoting atomization, unlike a carb that requires the fuel be siphoned through small orifices in the carb before it even atomizes .
A TBI is a very dependable cold starting system even in the face of -25 degrees and better.
I wouldn't worry about any timing chain problems at this point as it is a dual row chain and not the morse silent type. The dual row is used in roller cam engines because it is less prone to allow timing fluctuations due to design alone.
I would try spraying down the throttle and then try to start it first thing in the morning to see what you get.If it starts with a spray then fuel is lacking for some reason.
It would really benefit the diagnostic routine if you had a pressure gauge on the system to verify cold startup pressure or lack of, or slow to build pressure.
Better to diagnose than to throw parts at it.


One other option for cold startup fuel starvation (a presumptive test) would be to turn the key on don't crank, wait 2 seconds. This cycles the fuel pump by using the ECM 2 second pulse that turns the fuel pump on to prime the system. You can cycle the key 4-5 times. Be sure to listen to be sure the fuel pump relay is indeed cycling. Then after that see if you get a decent cold startup.
If that seems to help the startup situation the it is likely the pump check valve is not holding or the line in the tank between the pump and the fuel outlet line is leaking.


At any rate you really need to nail down if your cold start problem is fuel related.
Be sure the fuel pump relay will cycle and that it is powering the circuit
Get a fuel gauge and hook it up.
Stop guessing at it.
Well with a brand new dizzy and coil I don't think that would be the issue. However I am starting to believe the Check valve is bad causing fuel pressure bleed off.
 

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get somebody to listen to the fuel pump.. while you turn the key on.. does the fuel pump come on for 2 seconds at Key ON. then turn off.??

if not.. replace the fuel pump relay.. 89 should be over on the passenger side of the firewall under the hood.. it will have a small black wire that is connected to ground.. a ORANGE Wire that is hot all the time. a Green and white stripe wire.. DO NOT probe this wire with a test light.. i am giving you wire colors to identify the relay location.

at key on the ECM sends positive power to the Green wire with the white stripe.. that closes the relay for 2 seconds at KEY On.. then it turns it off if it does not see the Cranking signal from the ignition switch to the ECM.. and it will turn it off if it does not see RPM from the distributor Pin B on the 4 pin connector.

get your engine started... reach over and disconnect the fuel pump relay.. the engine should continue running.. if it dies.. then replace the 2 prong or 3 prong oil pressure switch/sender...

what.. the fuel pump relay is controlled only by the green white wire from the ECM.. when the engine is running the oil pressure switch which has 2 circuits on the 3 pin version will connect the outer 2 pins to power the fuel pump with the oil pressure up..

if its a lot of cranking cold but not so hot.. change the fuel pump relay.. repeat the test above.. key on 2 seconds of fuel pump operation.. cranking you should have fuel pump operation..

if you have not changed the engine coolant temp sensor. SU102 at AZ is under 20 bucks for the sensor and pigtail.. both the sensors and the pigtails go bad.. tell the computer that the engine is way over temp.. if you disconnect the coolant sensor you should get a code 14.. if you clear the codes and jump the yellow wire to the black wire and turn the key on you should get a code 15. this proves the wiring to the sensor has not failed inside the harness.

there is more to accomplish.. like setting base idle on the TBI..

engine at operating temp.. stuff the idle air bypass passage full of shop rag.. you should have a fairly low idle speed.. you want 1/2 to 3/4 turn of the idle stop screw above the point where the throttle blades bind in the bore and stick closed.. if you had access to a scan tool to look at live data..

engine warmed up to operating temp. coolant temp over 195F.. TPS voltage below 0.98 volts.(0.45 to 0.75Volts DC throttle closed). IAC (idle air counts ) 20 to 50 is the perfect spot for them. if your throttle shaft bore is worn.. you will have issues..
 

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Discussion Starter #16
Fuel pump is kicking on, If i "prime" the system it only cranks 2 or 3 times. I dont think i am gonna get under that as i run 15w-40 in it. It's 6 cranks before fire if i dont turn the key on position and back off 4-5 times. On a hot start it fires right up, youd think it was MPI. TPS is good, IAC is great, i did rebuild the TBI and didnt adjust base-idle. Do i need to do that? I think the pressure is just bleeding off somewhere.:confused::confused::confused:
 

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TBI motors usually don't have a fuel pressure test port..

the pump should make 25 to 27 PSI instantly when deadheaded at the filter..

what.. i usually keep an extra filter around.. with a section of proper fuel line threaded into one side.. a chunk of hose.. to hook my pressure gauge to..


this is a 10 second MAX test.. fuel pumps don't like to be dead headed..

do you have a digital volt meter that has at least a 10 AMP DC setting..

if so.. find the fuel pump fuse. remove it.. set the meter up... use the probes held lightly without spreading the terminals into the fuse holder... have somebody start the engine.. i like to see less than 7.1 amps..

you might want to invest in one of these.. since you use the full size fuses. 30 Amp Automotive Fuse Circuit Tester
some stores may also have the 20 amp version.. if they do buy both.

if you remove the fuel pump relay.. you can with some care remove the cover from the relay.. plug it back in. give it a squeeze to turn on the fuel pump without the engine running.. the fuel pump amp draw should be really stable.. not bouncing all over the place.

i have found so many pumps that the bushings are worn away. the armature just wobbling back and forth rubbing on the half shell field magnets..

1990 S10 Idle Surge fuel pump shafts worn - Album on Imgur


Throttle body setting..

engine off.. grab the throttle lever... open it slightly.. wiggle.. you should NOT have any front to back play.. or very very little.. the throttle shaft bores wear .. so instead of this.. (O) you get movement when you open the throttle ( O) to this(O ) this effects the angle the throttle shaft closes to..

if the TPS voltage is not exactly the same each time the throttle closes.. you will confuse the computer..

do you have any friends with a scan tool to display LIVE data stream on these systems... snap on MT2500s, OTC monitor 4000s, monitor extended.. extended monitors.. genisys. autoxray units, actron CP9110 versions.

do you have a digital volt meter?? so you can check the TPS voltage..
 

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Discussion Starter #18
Yes i have a digital voltmeter and have already tested the TPS. Its tested good. I will check the throttle. Fuel pump is new so i really hope it isnt the issue. Not expensive but just a waste of money. I dont have a scanner for live data and i dont know anyone who does. There is no SES or CEL light anymore. Annnnnnd when i pulled in my driveway i thought i would be funny and mess with my dogs so i went to give her some throttle and heard a pop from the engine bay. Thought it was back fire. But when i put it in park and gave it some revs i got nothing. I back down my drive and headed back up in the same mannor and nothing. Not sure what it was. I dont have a Catalytic converter (not that it would even have anything to do with it) Just not sure what would have made the sound. I check my plugs and they are fine. When going down the road and coming up on a hill i can put my pedal half way to the floor and still be losing speed. My engine doesnt gain rpm or anything just seems like its starving for fuel. I can hear the fuel pump kick on when i turn my key and i can hear the relay as well. Im just at a loss with no scanner.
 

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Discussion Starter #19
Retested my TPS, its getting .586 V at idle and 4.1-4.280 at WOT (key turnde to on and engine off of course) Shouldnt it be 4.5-4.6?
 

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that TPS reading is perfect..

can you verify that each time it closes it reads the same..


did you see about stuffing a rag into the idle air bypass passage to block it.

then adjusting T15 idle stop screw to a very low idle speed... pull the shop towel back out and the idle will surge.. don't worry.. grap the throttle and take the RPMS to 1500 to 2000 and hold it stable there for 20 seconds.. then slowly return to idle.. that gives the computer the time to relearn the idle air position. you can shut it off.. wait 10 seconds and restart it without touching the gas..

this is a manual that covers both TBI and PFI for marine applications.. but it is the same testing for your preobd2 system. there is some there that does not cover your system. but a great idea.. in the first few pages . look at the CLEAR FLOOD mode.. that is why you need to have the TPS at the proper position and NOT vary..

http://www.weindex.info/pdf/FuelSystem/9.pdf
 
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