I've run out of ideas how to get a truck running correctly. Its a 1982 Chevy pickup with a 1990-92 LB9 305 TPI engine.

It ran at one time as I've seen it driving but I bought it not running. They put in / removed some fancy alarm/remote start system and it never ran after that. After much trouble shooting I found the VATS bypass was labeled / installed incorrectly. After I corrected that the engine started but would only idle. The fuel psi at the pump is 50-60. After I put a new diaphragm in the regulator I get around 40psi at the fuel rail engine not running. At idle psi is 35-40 and goes up a little to 45 psi as revs go up(when I can get the revs to go up). I put on a new MAP sensor. The TPS tested good. I've checked for vacuum leaks.

After I rebuilt the fuel regulator the engine does run better. It now will run above idle if I very slowly open the throttle. There is just no power, if I open the throttle fast it boggs down and dies. Sometimes after it runs it won't start again for a few minutes. There doesn't seem to be any pattern to this, Hot or cold doesn't matter. As far as I can tell the ignition system seems ok. The manual I have does not say what the timing is set to. I have it set at 4 BTDC for now. That is with the timing adjust (TAN/BLK) wire disconnected.

I'm running out of things to check / replace. The ECM is a 7730 and it has a Hypertech sticker on it. The ECM itself is a remanufactured Cardone ECM.

I'm guessing the engine is a 90-92 because it has a serpentine belt drive and alternator on the drivers side, has a MAP instead of a MAFS and the ECM is a 7730. The last two are for 90-92 models as far as I can tell.

As I said I'm out of ideas. I have a higher PSI fuel pump 60-80psi, the one that came on the truck, and I'll put it back on today but I don't think that's the problem (I didn't have a fuel psi test gage before I bought the new pump, wasted $120 I think on the new pump).

Does anyone have any ideas?

Thank you
Doug

 

did you check the throttle position sensor yet? otherwise sounds like it is probably in the wiring somewhere

 

As I said in my post I checked the TPS as far as the oms readings go and it was ok. That said I need to check the actual voltage sent to the ECM. As I understand it it should be .54v closed and 4-5v wot. I'll check that today.

Also, I was checking the fuel pressure incorrectly. I did not disconnect and plug the vacuum line to the regulator. I will recheck that.

Ya I'm worried about the wiring be so far it checks out. Also I guess I need to ohm out the injectors. After reading some posts here it seems they go bad often. to tell the truth, at $80 per injector I'll buy a carb intake and put on a 600cfm holley I have. Get rid of the ECM and go back to the 1960's.

Honestly I think thats easier said than done. But I'm not putting more money in this TPI setup. Will a Edelbrock, Wieland ect... manifold bolt up or does it require a head swap? Just frustrated, I'm pretty good at engines, no pro but I've build a few. 454's 351w 327's but all old style except the 454 that was TBI.

Last problem--The ALDL won't read. Maybe its my ODB1 scantool. No the check engine light is not connected so I can't read it that way. It comes off a different harness

Thank you

 

Check the injectors for sure, noid lite and OHM's. If you need injectors check with Southbay - https://www.thirdgen.org/forums/member.php?u=88662 I got a great deal from him.

 

Ok, checked the TPS and its correct. rechecked the fuel PSI and its 40psi running, goes up as rpm increases to 45. RPM will only got to about 3000 if I go VERY VERY slowly, after that it will die. If I open the throttle fast it dies. Fuel psi stays around 40. so. new fuel pump, MAP, TPS is ok New ICL valve, New fuel regulator, no vacuum leaks. Set timing to 6 BTDC, tan/blk timing wire disconnected.

I know all of you hate this as I've just changed parts. I've done all the trouble shooting I can but the $hty Haynes manuals don't give much info.

So far, new fuel pump, MAP, TPS, AIC(Idel control) ,Regulator diaphragm , all fuel lines.

what am I missing? Could it be the ignition module?

Again idles great...........If I very slowly open the throttle it revs to 2500 or so rpm then dies. If I open the throttle just a little fast it dies.

Still need to check the oms on the injectors it I can figure out how to remove the clips. I very seriously doubt its the injectors.

thinking strongly of just putting on a 600 holley and selling all the new parts 50%off on ebay.

Thanks doug

 

Ok, checked the injector ohms. one was 2.9, one was 6 and another was 9.7. the rest were 14-16 ohms...could this be the problem?????

I hate to spend a few $100 if its not the problem. if it is what injectors to buy. It has full headers and a hypertech prom.

If a set of injectors is +500 then I'm going to revert to a carb.

Thanks
doug

 

TPIs' use High impedance injectors. 14-16 is correct, the two with lower impedance are bad or wrong! The ECM Injector drivers will not work correctly with low impedance injectors. Are you using the original LB9 distributor?

 

if your injectors are showing that low the ecm will shut down that driver for that bank of injectors. it does seem like a fuel pump problem when this happens. I had put a tpi in my 82 camaro and had a wire short cuzing it to run on only one bank. it would idle great but die if you gave it throttle. start there. if your close to fargo i got a tpi installed in my 92 truck. i'd be able to get it fixed for you!

 

A set of injectors through southbay and other places are less than $200. I think I saw $170 in a post very recently.

It sounds like, the injectors are a good chunk of the problem if some are ohming that low. Don't go cheap, replace the whole set or else in a few months you will be back in there doing it again when the others go.

 

could be ignition module or pickup also.

 

I got a set of injectors from southbay. 21lb i believe and cost me under 200 and man did they help with the idle quality. will do bussiness with them again.

 

Thanks guy, lots of good info. I didn't know I could get a set of injectors for <$200. Next question is what injector to use? Stock or or ones with more lbs/h. I'll have to look and see what stock is.

The 305 has full length headers and the ECM (7730) has a Hypertech sticker on it. I cant say for sure if it really has a Hypertech prom or not.

Given that info, What lbs/h injector should be used. I really don't want a gas hog but a little more power is always great.

Thank you all
Doug

 

stock for 305 is 19 lb/hr as far as changing them unless mods necesitate it I wouldn't go past 21 lbs if it has a healthy cam and better heads it shouldn't need any more. which really 19 lbs should be fine for pretty much stock.

 

OK guys, I ordered a set of bosh III's 19/lbh at southbay for $155 with the adapter so they'd fit correctly. If the ohms test is correct them I have at least 2 bad injectors. so I may as well change all 8. Hope to get the new ones by Friday.
The guys at southbay recommended to stay with the 19lb injectors
I'lll let you all know what happens.

Thanks all
Doug

 

Yes its the original distributor, I really don't know how to test the ignition but I can say the spark looks good at the plugs.

Doug

 

How long was this thing sitting when you bought it? Is the TPS VOLTAGE Correct? Should be .54 at idle and around 5.0V at WOT. Put your volt meter on the TPS and move the throttle, does the voltage rise smoothly as you open the throttle or does it spike up or drop to zero as you move the throttle?

TPS Voltage adjustment (Early cars only with adjustable TPS).

There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires.
You can either buy a special harness connector that breaks these wires out (from Mid America), or gently pierce the insulation of
the wires with the pointy prongs on your volt meter. You can also stick a paper clip into each of the two top locations of the
connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.
• Turn the ignition to the “ON” position without starting the engine.
• Loosen the TPS Torx adjustment screws.
• Set your volt meter to a low scale DC volt setting that will accurately read less than 1 volt.
• Measure the voltage between the two top TPS wires.
• Adjust the TPS by rotating its position until you get a reading of .54 volts.
• Tighten the Torx screws and recheck the voltage. Re-adjust if necessary to make sure voltage is right at .54.
• Turn the ignition “OFF.”

Thanks to: Lars Grimsrud
Colorado Corvette Crazies (CCC) for this internet posting.

Also check the voltage as you open the throttle, as described, voltage should climb and descend smoothly from .54 V to peak at about 5.0 V

 

Yes the TPS is adjusted correctly

Thanks

 

Found two bad fuel injectors. Got a set of Bosch III from Southbay and it runs great.

Thanks all
Doug