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Old 10-29-2013, 03:25 PM
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vortec fuel injection to carburetor

Im new to the site and am looking for advice. I took the drive train out of a 2001 express 2500 because it was free lol the 5.7, 4l80e, steering column and cluster and put it in a 1985 c/20 thinking it would nice haveing fuel injection in an older vehicle. I used everything from the van that i cud except for the rear o2s and cats, and replacing all sensors the updated fuel injection and factory intake fuel pump. According to gm the fuel pump should put out 65psi but changing 2 pumps it wont go past 55 and always throws 2 codes random multiple misfire and mass A/F. I think im tired of chasing the FI gremlins. I saw that u could use a carb intake and also use a return style fuel pressure reg. but they talk about changing distributors to HEI, but do i have too. the dis ive got is already set up with all the msd goodies and im gonna keep the computer to run the trans and cluster im assuming this is possible since it will still reference crank position of the sensor and cam position off the sensor in the distributor. if anyone could help with this or point me in the right direction would be great i miss driving my truck lol Thanks David

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Old 10-29-2013, 04:34 PM
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You are gonna have to retain & figure a mounting solution for the TPS(throttle position sensor).The 4L80E will have to have this input as well as the TCC lockup.You think you got Gremlins now??? It can be done,but,it's quite a task.You would be better off to prolly set the engine up as a carbed system & use an aftermarket controller for the trans.It doesn't sound like you have major problems with the EFI.Where are you reading the fuel psi from?
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Old 10-29-2013, 04:39 PM
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55 psi is about all your gonna see @ idle.It should increase as you open the throttle.If you psi is indeed low,then you are getting a lean condition setting the codes.Are you tuning yourself?
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Old 10-30-2013, 08:21 AM
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vortec

Thanks for the responses, im reading it off of the fuel line before it goes to the spider assembly and honestly i didnt think it would require tuning since basicly swapping chassis. I'll recheck pressure at part throttle and go from there. And to the other response if all else fails i was gonna convert it to carb i'll research the tps mounting Thanks again
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Old 10-30-2013, 01:38 PM
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Quote:
Originally Posted by david1979 View Post
Im new to the site and am looking for advice. I took the drive train out of a 2001 express 2500 because it was free lol the 5.7, 4l80e, steering column and cluster and put it in a 1985 c/20 thinking it would nice haveing fuel injection in an older vehicle. I used everything from the van that i cud except for the rear o2s and cats, and replacing all sensors the updated fuel injection and factory intake fuel pump. According to gm the fuel pump should put out 65psi but changing 2 pumps it wont go past 55 and always throws 2 codes random multiple misfire and mass A/F. I think im tired of chasing the FI gremlins. I saw that u could use a carb intake and also use a return style fuel pressure reg. but they talk about changing distributors to HEI, but do i have too. the dis ive got is already set up with all the msd goodies and im gonna keep the computer to run the trans and cluster im assuming this is possible since it will still reference crank position of the sensor and cam position off the sensor in the distributor. if anyone could help with this or point me in the right direction would be great i miss driving my truck lol Thanks David
It's looking for the rear O2s and by default of them missing the cats. so it's running in limp home mode. The fuel pressure is managed by the computer imposing a run to off to run cycle on the pump motor. Probably part of limp home you're not going to see any more pressure. The Vortec is an OBDII system which is much more sensitive than OBDI in regard to what it will tolerate in mods.

Change to a carb and HEI is simple enough, the best way to handle the 4L60E is with a stand alone controller rather than hacking the OEM computer <<< The US Shift Transmission Control System >>> . Here's some light reading <<< Testing the Latest Transmission Controllers - Car Craft Magazine >>>

All this depends on your electronic knowledge and abilities for converting your existing computer to simply run the thransmission. This can be done.

Bogie
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Old 10-30-2013, 02:14 PM
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You will need someone with tuning capabilities to go into the PCM & disable the rear O2 sensors.You may still need to do some tweaking once in there.I think I would try to stay EFI if @ all possible.
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Old 10-31-2013, 09:34 AM
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Joker is correct about the fuel pressure.
This is correct, the vaccuum referenced FPR brings the pressure down at idle(high vacccuum) try measuring your fiuel pressure with the Key On Engine Off(KOEO) it will read over 60 psi probably.
If you do check it while idling, hook up your gauge and give thethrottle a quick stab wide open. You should see theFP spike up as thevaccuum referenced FPR reading the pressure increase(vaccuum decrease) as the throttle opens quickly.
Checking the fuel pressure will do nothing as the engine vaccuum will still be high(low pressure inside the manifold) so teh FPR will still read closer to 55psi. You need to have your gauge hooked up and using your hand, twist the throttlewide open and let it snap shut. The sudden drop of vaccuum(sudden rise of poressure) will cause the FPR to raise then lower the presssure. Slow throttle movements are useless for diagnosis.

So long as all you did was take the engine/trans out and drop it in the older vehicle, you shouldnt need tuning. You will have the SES light because of the rear O2 sensors missing, but this will NOT affect the way the engine runs. I have a 97 with the same exact scenario that runs fine.

When you added the MPFI spider, are you sure that you got each spider leg into the correct intake runner. Common issue of guys getting thewrong spider in thewrong hole.

ARe you sure you have the MAFS(mass airflow sensor) plugged in? If not plug it in, if you do try un plugginbg it and driving in Speed Density mode.

Random missfires can be caused by anything, plugs, wires, cap rotor, carbon buidlup in the chamber.

Since this engine and trans came from a 2001 van, you shoudl have the silver 0411 PCM that has the dual 80 pin connector. This is the desirable PCM

How does the engine run when you go to WOT(wide open throttle)? Get it on the road and hold it WOT for at least 5-6 seconds while in gear. The PCM doesnt read the O2 sensors after the PCM enters PE mode after the PE timer counts off 4 seconds. If it runs fine at WOT, you have an issue with the precat O2 sensors or their associated wiring.
.
peace
Hog
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Old 11-02-2013, 10:59 AM
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vortec

Thanks for the input hog.
Im gonna put the cats and rear O2s on just for the heck of it just so i covered all my bases. Now i did follow the directions installing the spider right down to crossing the lines in the correct pattern. I did not know about the vaccum pressure resulting in change of FPRs. I will look into that again this wknd, but what i have figured out is that ive done the key on and off cycle test for leak down and stays constant at 55psi. I had a friend come by with his scan tool and sounds like what uve been talking about because at idle bank 1 will run 12% pos and bank 2 will be 15% neg but as soon as u hit the throttle the rolls reverse. ive checked for vaccum leaks with the smoke machine and the only thing that i found was the case for the IAC valve slightly leaking so replaced that, again just to be on the safe side. And the pump has been replaced twice due to burning up the first getting it to run and both r delco. As far as the MAF is concerned i have tried to run the truck w/o it being plugged up but it seems like it only running at about 60%. And as far as the engine goes i freshened it up from top to bottom with the addition of new cylinder heads because both of them had hairline cracks. If that helps with any more input it wud be great. And i will check the FRP from ur instructions
Thanks again Dave
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Old 11-03-2013, 01:32 PM
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Hmm, I dont know whats going on if you see 55psi with the engine off and the fuel pump running by cycling the key. They you should see around 62-66 psi under such conditions and the manifold vaccuum brings the pressure down to around 56psi while idling.

I saw an add in the new Hotrod where IIRC the new Speed Demon carbs, the ones that are all smooth and polished looking. They have a bolt on TPS assembly so you can run an electric 4l60e/65e/70e or 4l80e/85e trans. They also include the attachments for the 200r4 and 700r4 TV cables.


OK, here stick with me for a second. The LD Vortec 350's use the smaller 1 7/8" headpipes into the cats, while the 3/4 ton L31's use the larger dual 3" headpipes into larger cats.
Bank 1 is for the exhaust from the drivers side of the engine, while Bank 2 is usally reserved for teh passenger side exhaust gasses.

Check out this picture of the LD L31 and HD L31 exhaust side by side.



As you cann see when doing a swap, it is easy to mix up the proper Bank 1 and Bank 2 fueling because of teh differences between the 2.

When I did my marine intake swap into my 97 L31 Vortec 350 truck, I had the 1,3,5,7 injectors being fed by the 2,4,6,8 PCM injector drivers. At idle I was getting split BLM's with unburned fuel and eventual flames shooting out the sidepipes which exit before the pass. side rear tire. But as soon as I would touch the throttle, the flames would stop as the. The same scenario would happen if the Precat O2 sensors were miswired.

UNplugging the MAF should cause rough running. IIRC unplugging it will usually cause it to stall.

Does the engine run any different when the running in Open loop(dead cold start) as compared to Closed loop(after a bit of warmup-where the O2 sensors are being read by the PCM)?

The rear O2 sensors wont affect the operation here, you can get them "tuned" out via PCM recalibration. I have them shut off in my rcsb L31 truck, but havent turned them off yet in my 97 ecab. I tune with Tunercats OBD2.

Did you try and pull the codes out of the PCM?

WHat are you using for exhaust? Do you have the EGR bung in the drivers side exhaust manifold that feeds the EGR at the front of the intake manfold? It should be a pipe with a black fabvric covering that screws into the front of teh intake manifold and into the drivers side exhaust manifold.

ARe you using the van headpipes and the supplied precat O2 sensor bungs, or are you using exhaust pipe with the O2 sensor bungs welded on for you to use?

Did you have any issues when restabbing the Vortec distributer?
HAve you done a CASE relearn (Crankshaft Angle Sensor Error relearn) aka crank relearn. Supposed yto be done when new cranks, timing chains, engines into a vehicle. It involves a scan tool which does a crank relearn, you plug in the machine, follow the direction and hold the accelerator on the rev limiter and then release the pedal and the relearn is done.

Also since you had the distributer out when you did the heads, you must set the CMP retard, aka camshaft sensor retard. This isnt timing advance, it is set by clocking the distributer body until the scan tool reads plus or minus 2 while either revving the engine over 1000rpm after each clocking of the distributer. You simply loosen the distributer holddown slightly, clock the body rev, check until it reads + or- 2, then tighten the hold down.

Any info could be helpul.

peace
Hog
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Old 11-05-2013, 07:59 AM
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Vortec

Thanks Hog
OK about 2 mos ago we tried using the GM tech 2 scan tool on it and the pre o2s r in the correct locations the distributor is set correctly. And for the crank relearn it failed to do so I'm assuming because of the fuel pressure. The exhaust manifolds I didn't use what I opted for was a performance upgrade that wasn't listed for a van but for a truck which is short tube headers from heddman and it allowed me to use the egr tube for the egr. As for the cold start it does seem to run just alittle better but not much and doesn't take long for the chk engine light to start flashing with 2 codes for random cyl misfire and a mass airflow code which the MAF I've swapped out twice and as for unplugging it there Is a slight difference but not much. I do see an abbreviation that u used I've not seen before what is IIRC? And as far as rechecking the fuel pressure like u suggested last post I wasn't able to due to bad weather so I can hopefully chik that this wknd , I think I covered Ur questions let me know what u think .

Thanks again for all your input
Dave
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Old 11-05-2013, 10:21 AM
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Sorry man, IIRC means: If I Recall Correctly, meaning if my memory isnt failing me.

So you are getting a flashing SES light, that happens when random missfires are detected, and unburned fuel enter the cats can cvause them to melt.

Your shorty headers will be fine, no matter what they are from.

Plugs are to be gapped at 0.060" on these engines.

The PCM has no way of knowing that the fuel pressure is low directly, it will only make a difference if it causes the engine to not run correctly.

Look in the fuse block for ENG B and see if its blown, but check all the fuses.

Be usre to have a good cap and rotor, wires, plugs. I have seen many many missfires on these engines caused by bad ignition parts. Many time new plugs clears up issues. Use stock type only, no fancy multi spark units or anything.

It's tough to diagnose over the interwebs, but those are the basics.

Do you have the brake switch hooked up to the PCM?

peace
Hog
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