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Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
First let me say this is an engine swap using a 1988 L98 engine and a Painless wiring harness. My car will start fine and runs fine when cold Will not start back up warm unless I use starting fluid.The injectors is not firing when warm (using a noid light). What I want to know is what would send the ECM a signal not to fire the injectors when warm? Or what information is the ECM not getting. I have change or checked all of the things listed below. Plus I have checked everything that anyone on the fourm has suggested. I have been working on the swap since April of 2025. I desperately need some help!
NO CODES
Fuel pressure 45 psi starting 40 psi running
Injectors, I sent the original injectors and had the refurbished, Ohms reading 16.7 cold, and 16.0-16.5 hot. Holds pressure with only a slight drop, it takes over 30 min to go from 40 psi to 0
Cold start injector – resistance 3.3 cold, 4.3 hot
Rebuilt fuel pressure regulator and added an adjustable fuel pressure regulator top
MAF replaced with 2 new, voltage correct– seems to be working fine, engine changes and code 34 when unplugged.
TPS, voltage correct
New coolant temp sensor - checked resistance hot and cold - good
New MAF burn off relay
New fuel pressure relay
New electric spark module
New ICM – 3 new, checked good at part store
New coil
New rotary button
New distributor cap.
Distributor coil pick up resistance 782 when cold 862 when hot
Pulled spark plugs and check gap (good) and for being fouled out ( none fouled)
just check the fuel pressure goes from 45 psi to 0 in about 5 sec. I assume that something is bleeding. but how do I find the injector that is. I smelled the vacuum line to the fuel pressure regulator and didn't smell any gas. I'm going to change fuel pumps again to make sure it's not the check valve.
question. I know that the injectors are not pulsing. the truck is not getting any gas. So what is causing that
As mentioned pull up the csi to see if it’s it causing the flooding. If not you can tear down the tpi and raise the rail or prime multiple times and check plugs for being wet.
I have already checked the plugs to see if they were wet, none was. do you really think it's flooded sense it starts so quick with just a small squirt of starting fluid and if I wait 10 to fifteen min it will start. I want to thank you for all your help
One question not asked was does pressure hold with the return pinched or can you pinch the return in your application? I’m really not sure where the fuel is going when the pressure drops .
Can't be that. If it was, a shot of pure oxygen would start it up, NOT a shot of fuel.
ECM is grounded properly
Can't be that. Grounding the ECM is important for sure; butt it won't be poorly grounded during starting, then magically repair itself after a shot of ether.
I want to run a ground directly to the battery
Great. Won't hurt. Also won't help. That ground doesn't change in between starting and running.
the flooding
THERE IS NO "the flooding". If there was, flooding it with YET MORE FUEL, wouldn't make it start RIGHT UP.
Put aside the "maybe it's this maybe it's that maybe the aliens are testing the humans' problem solving skills" and EMPLOY SOME LOGIC. That logic is, if it won't start "normally", butt if you squirt in some ether it starts, then IT LACKS FUEL AT STARTUP. C'mon d00d, it's just a car, it's NOT THAT HARD. Use logic, reason, and common sense (which I fully realize, its name is a bit ... misleading ...) to get to the root of the problem. Which is, NOT ENOUGH FUEL AT STARTUP. Logic. Reason. Observation. See my signature.
Ignore all that s*** about leaking injectors. That's NOT the problem if it starts up by adding more fuel. The Problem is, fuel is GOING AWAY at that time, not that it's appearing in excess. Screw your head on straight and look in the right direction.
I know nearly nothing about TPI.
Does the following fit his condition? OP said,
My car will start fine and runs fine when cold. Will not start back up warm unless I use starting fluid.
yes it starts with a small squirt of starting fluid
the fuel pressure goes from 45 psi to 0 in about 5 sec
if I wait 10 to fifteen min it will start
Again, I know nothing. But to me, what fits this condition is that a leaky injector(s) is putting fuel into the intake when he shuts the engine off WARM. It won't restart because it is flooded. The warm engine takes about 10-15 minutes to evaporate that fuel and then he is able to restart the engine. Liquid fuel does not ignite, therefore a small shot of starting fluid (very well atomized) allows the engine to start.
I know nearly nothing about TPI.
Does the following fit his condition? OP said,
My car will start fine and runs fine when cold. Will not start back up warm unless I use starting fluid.
yes it starts with a small squirt of starting fluid
the fuel pressure goes from 45 psi to 0 in about 5 sec
if I wait 10 to fifteen min it will start
Again, I know nothing. But to me, what fits this condition is that a leaky injector(s) is putting fuel into the intake when he shuts the engine off WARM. It won't restart because it is flooded. The warm engine takes about 10-15 minutes to evaporate that fuel and then he is able to restart the engine. Liquid fuel does not ignite, therefore a small shot of starting fluid (very well atomized) allows the engine to start.
Right or wrong?
I figured it was a leaky injector but I pulled the plugs and they were dry. How do I find the one or ones that is leaking. to expensive to replace all of them.
OK Sofakingdom. I have been looking this probem head on for 10 months.I have changed everthing that would cause it to not start when warm. I have done everything that was told to me to do on this fourm and I'm no closer than I was 10 months ago.I just drove the truck and it ran like she i t. I have a 40 chevy with a l98 tpi that I've had for 30 + years and never had a problem with it.
# 9 what?
fuel pressure is holding for 30 min before it starts to drop from 40 psi.
can the distrubutor pickup be bad even though the restistance reads good hot and cold. that is the only thing I haven't changed
# 9 what?
fuel pressure is holding for 30 min before it starts to drop from 40 psi.
can the distrubutor pickup be bad even though the restistance reads good hot and cold. that is the only thing I haven't changed
what changed from
the fuel pressure drop ? He was referring to post #9
# 9 what?
fuel pressure is holding for 30 min before it starts to drop from 40 psi.
can the distrubutor pickup be bad even though the restistance reads good hot and cold. that is the only thing I haven't changed
are you missing injector pulse or spark or both when warm engine?
