Fuel pressure is holding over 30 min before droping from 40 psi
can the distributor pickup be bad even though the restistance is good hot and cold. that is the only thing I haven't changed

 

that’s good, what changed to make fp hold ?

 

I don't have a clue. I drove the truck twice yesterday and afterwords I happen to look at the fuel pressure gauge and it was holding. I did notice that just starting the truck and letting it run for a min ot two it would start back up within 10 to 15 min. driving it and getting the temp up to 180 it takes up to an hour to start back.unless i use starting fluid.
what about the distributor pickup?

 

If you're not getting injector pulses while cranking, it would suggest that the ecm is not seeing any distributor reference pulses. Does the SES lamp flash 12 during cranking (with ALDL bins A-B shorted)?

What prom is in the car?

With $32B bins, it is possible to log the crank fuel pulse width: https://datazap.me/u/tequilaboy/anti...15-123-113-122

Note: in this example the cranking fuel tuning is a bit exaggerated and ramping up quickly in order to facilitate quicker starting, but it still took about 1.5 seconds here.

This turd took 3 seconds to start: https://datazap.me/u/tequilaboy/cold...k=5-26-7-25-16

And another: https://datazap.me/u/tequilaboy/cold...rk=29-50-39-27

With $6E bins, you can only see the running fuel delivered, but at least it can offer a clue as to what is going on with the crank fueling.

 

I'm not getting injector pulse when cranking warm. cold I am getting injector pulse. that's why I was asking about the distributor pickup. I'm not sure if it would effect the computer or the injector pulse. I do have spark and it starts fine with a little squart of starting fluid

 

I thing this is the prom . sorry about how large it is

 

That’s what’s considered a memcal, memory calibration. With a prom on one side and netress on the other

 

Just clarifying with the squirt of starting fluid, it starts and stays running or does it eventually stall when the starting fluid is all consumed???

 

it starts and stays running

 

I don't know what that means. are you saying I need a different prom. if so can you recommend one.
I have another ECM and a aftermarket prom that I tried and the truck does exactly the same thing

 

Strangely, I haven't seen any mention of VATS. Since this is an engine swap and not a Corvette (apparently running ABTS 4767) what have you done to disable VATS?

 

This thread is the beginning of the saga in June last year. 78 posts. Many of them pertain to Code 46, Bypasses, the Timer.shop signal generator, Painless Harness VATS solutions, different PROMS. VATS has been discussed, but it's hard to tell with this guy whether VATS is or isn't still an issue.
This other thread of his has 61 posts in it.
And this is a thread regarding VATS bypasses. Only 8 posts. The engine was running, but then it wasn't.

I think the current issue is that it starts ok when cold, but won't restart hot. Again, it's tough to tell with this poster what is really going on. Several guys here have participated attempting to help him figure this out. Their patience has been notable.

 

Continued on tgo

https://www.thirdgen.org/forums/engi...-starting.html

 

This has probably been mentioned, but perhaps it hasn't. If an injector is leaking, causing flooding, holding the throttle wide open puts the system in Clear Flood Mode which turns off the injectors. So try cranking it with the throttle WOT and see if it fires quicker.

Another symptom of "flooding" is it will fire with visible black soot smoke.

And a last thought: You aren't by chance trying to start it with the throttle open? That puts it in Clear Flood Mode which will result in "no injector pulses". Or: Have you checked that the TPS voltage is below 2.0-ish volts when cranking? The actual Clear Flood Mode voltage is higher than 2.0, but not by much. Be sure the voltage on the blue wire at the TPS is <2.0 when cranking.

 

I have installed a vats bypass. in the beginning the truck would not even start hot or cold.
I posted that the fuel pressure was holding and it takes over 30 min to blead down
I'm not trying to start the truck with the throttle open. I know the injectors are not firing when warm. My question is, what would be wrong for the ECM not to fire the injectors

 

TPS voltage greater than appx 2.0 Volts?

 

I'm not sure I'm doing what your asking. are you talking about the voltage at the TPS? the voltage at the TPS blue wire is .54. when cranking it comes up to .54. engine hot or cold. and when the engine is idling it stays at .54 until I give it some throtle

 

The question being asked is The ECM going into clear flood mode as long as the throttle is 80% or higher or around 4v feedback the ecm shuts off injector pulse. So when the engine is warm have you tried starting the engine with the gas pedal floored ?

 

yes I have tried holding the throttle open more than once.
the only two things I haven't changed is the knock sensor and the oxygen sensor. does it make any difference what side the knock sensor is located? and would the knock sensor keep the injectors from firing?

 

The knock sensor is not going to keep it from running. My C4 had a bad Knock sensor on it when I bought it, the power seemed down and all eight cylinders were consistent. A new knock sensor made the car feel new again.

Did you touch or modify the EGR system on the 1988 L98 engine? This engine does not like the EGR disabled or broken, it will run much hotter and require that you run premium fuel to keep it quiet. If you are not going to use the EGR then it HAS TO BE removed from the code for the engine. It is not hard but requires specialized knowledge to do it.

I have had a 1988 C4 for about thirty years and have had lots of fun with it. The L98 is a strange beast that requires special knowledge. My fuel supply line rusted internally and was virtually closed off. I had gasoline at 42-44 lbs pressure but nowhere near enough volume for the engine to run. After replacing the fuel lines with a rubber hose the car started and ran great.

Injectors were replaced as a set and that stopped the gas leaking from the injectors. The injectors are batch fired so expect to see multiple cylinders all getting gas at the same time. I found a great deals on injectors at South Bay Injectors 516-442-4707 as they are here on the East Coast and have great prices.

The electrical connections on the injectors are important to be kept clean and secure. If I am not mistaken the injectors all have 12 volts supplied to them and the injectors are "pulled to ground" to activate them. The 12 volts is live to the injectors when the engine is in the "Run" mode. No voltage, no injection, take a good look and verify the injectors are (batch) firing.

I have a Snap On MT2500 and it is indeed very handy on OBD1 vehicles. There is one cartridge that is priceless for the MT 2500, it is the one that works on GM's early (BOSCH) ABS systems.

One of the biggest problems I have had with my 1988 C4 was a low voltage situation that kept the electrical components from working due to low voltages. The Fuel pump NEEDS to have full power, the fuel pump relay needs to have the voltages verified and corrected if needed. Since you are using the engine in a different vehicle the electrical

Your Fuel Pressure Regulator seems to be working okay. I would stick with the stock pressure range and not push the higher pressure into the system.