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rack 09-04-2012 02:15 PM

1990 Chevy TBI runs very rich
 
Hi guys,

Recently I got my 1990 Chevy Suburban imported from USA. I like it very much. :)
As every old car, there are some problems with it.
It is SBC 350 with TBI.
First, it runs very rich (at least I think so). I have to pres accelerator to start it, there is black smoke, very noticeable gasoline odor, rough idle and it often die on D or R.
I plan to buy TBI rebuild kit but rockauto supply two kits, one for TBI100 & TBI200, the other for TBI220 & TBI295.
How can I identify what TBI is in the car?

Also, I will be very grateful for any tips and suggestions on what to look or set in order to get proper operation.

Thanks a lot for your help,
Ivo

dwb812 09-04-2012 04:23 PM

Before you buy a rebuild kit.
 
You might wanna check a couple of things before you buy a kit and tear into your TBI. The fact that you say you have to "step on the gas to start it" indicates a problem with the mixture at cold start. That can be an issue with the MAP sensor, an oxygen sensor, or other sensors that send info to the "computer" . The chance that the starting issue is in the TBI itself, at least in my experience, is slim.

Also, most of these set ups have a brown wire that is disconnected when timing of the engine. It is usually either up under the dash behind the glove box or by the distributor at the fire wall. If that is discinnected your engine will not automatically advance the timing when in D or R or when load is applied to engine in general. Might be worth a look as well.

LATECH 09-04-2012 04:35 PM

Coolant temp sensor is a very common problem on those, and it sounds like your problem. Check for codes. Repair accordingly.

rack 09-05-2012 10:30 AM

Thanks guys,
I will check these as well.

Unfortunately, today fuel pump died :(, so I have to wait some 15-20 days for new one.

I will let you know how it is going.

Thanks,
Ivo

oldbogie 09-05-2012 12:26 PM

1 Attachment(s)
Quote:

Originally Posted by rack (Post 1588349)
Hi guys,

Recently I got my 1990 Chevy Suburban imported from USA. I like it very much. :)
As every old car, there are some problems with it.
It is SBC 350 with TBI.
First, it runs very rich (at least I think so). I have to pres accelerator to start it, there is black smoke, very noticeable gasoline odor, rough idle and it often die on D or R.
I plan to buy TBI rebuild kit but rockauto supply two kits, one for TBI100 & TBI200, the other for TBI220 & TBI295.
How can I identify what TBI is in the car?

Also, I will be very grateful for any tips and suggestions on what to look or set in order to get proper operation.

Thanks a lot for your help,
Ivo

Runing rich on idle can have several causes, for example:
- Throttle Position Sensor failed or misadjusted
- Idle Air Controller (IAC)
- Coolant Temp Sensor
- Fuel Pressure Regulator
- Obstruction in the fuel return lines to tank
- Pressure build up in tank due to failed venting system

This list can go on, if the error is in sensing it should be showing the CEL light then you can down load the Check Engine Codes from the connector under the instrument panel by your knee. You really need a maintenance manual as these electronic things are difficult if you're going at it with no info.

To determine the Rock Auto kit you need to rebuild the TBI you need to get the injector part number which is readable on the tops of the injectors. Here's a list of what goes to what.



Bogie

rack 09-05-2012 03:02 PM

Thanks a lot Bogie.
I am getting better picture.
I have Chiltons manual which describes sensors and test procedures. I will perform some test tomorrow. Unfortunately cannot run the engine because of faulty fuel pump.

Ivo

oldbogie 09-05-2012 05:55 PM

Quote:

Originally Posted by rack (Post 1588592)
Thanks a lot Bogie.
I am getting better picture.
I have Chiltons manual which describes sensors and test procedures. I will perform some test tomorrow. Unfortunately cannot run the engine because of faulty fuel pump.

Ivo

In the tank fuel pump a that. More fun to change these out.

Bogie

Caprice Sleeper 09-06-2012 07:12 PM

I had the same truck with the same issue. when the coolant temp sensor goes bad on those trucks it will run very rich and act just like you describe. It will also NOT set the check engine light. I unpluged mine and it was able to run but it then set the engine light for a coolant temp sensor curcuit fault. I guess they designed them to only monitor coolant sensor curcuit and not coolant sensor range/performance. Try unpluging the sensor(I think it is the two wire sensor to the right of the thermostat housing) if it will run on it's own after you unplug it(unplug with engine off) then you found the problem. I unpluged mine and drove it for about a week before I fixed it. It will run just a bit rich instead of pig rich like yours is now, won't hurt anything. Just remember if you do unplug the sensor you will trip the engine light and will need to clear it or disconnect the battery if it doesn't go out. Hope this helps.

Jay

Caprice Sleeper 09-06-2012 07:19 PM

O yeah I use to monitor those trucks with a snap on scanner when I thought the coolant sensor was bad and if it was the sensor would think the coolant was like -30F when it was over 80F outside. The unplug trick was just something I did when I no longer had a scanner that had live data.

rack 09-07-2012 10:18 AM

Thanks for the tips Caprice Sleeper,
I will try this first as soon as I start the engine. No fuel getting there :(

Can someone explain me how to check fuel pump?

I have three wires going there. Black, which is ground and gray and purple.
One of them is for tank sending unit I guess.

Also, on the car side, I have to measure between ground and connector leads one by one, is that correct?

Thanks for the help,
Ivo

T-bucket23 09-07-2012 02:41 PM

My bet is the coolant sensor. I have replaced a bunch of them. I think when open they default to -20*f.
Before you go dropping the tank, check at the harness near the tank for power and ground. It is very common for the connectors to fail and the grounds to rot off the frame. I have an old headlight I use to check for power, a test light does not draw enough current to show a bad connection all the time.

rack 09-23-2012 12:37 AM

For the archives and to keep you informed :D

Thanks for the help guys.

I did not have enough patience, so I dropped the tank to discover new fuel tank sending unit and pump. I cleaned all connectors and ground, test with test lamp, everything check good. Put the tank back.

On the engine compartment, I found two bad spark plugs wires, changed with some I have on hand, disconnect coolant temperature sensor and truck started and runs much better. I sill have to press accelerator to start it but then it idles fine.

Because I am not in USA, now i am waiting for new wires and distributor cap, temperature sensors and some other parts.

Can some one point me to good online store for electrical connectors? I need to replace a lot of them.

Thanks again for your help, I will keep you informed on the work I have done :-)

Ivo

rack 10-08-2012 12:28 PM

Hi guys,
I changed temperature sensor, put new air filter and air cleaner gaskets (there were not any :confused: ), and things looks much much better. The engine runs almost normal, starts much easier and there is no this black smoke out of exhaust :)
Thanks a lot for the help :)

Next step is to change distributor cap and rotor, spark plugs and wires.

I have some additional questions. Since I am going to disassemble and clean TBI, is it good idea to change injectors as well?
This one looks good deal:
GM THROTTLE BODY TBI FUEL INJECTOR SET 1987-1996 5.7 V8 GMC CHEVROLET PICKUP VAN | eBay
What do you think?

Thanks for the help,
Ivo

va4cqd 10-08-2012 01:52 PM

for that price it wouldn't be a bad idea to change the injectors. i would recoment changing the fuel pressure regulator diaphragm while its apart


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