BaggedMerc

Hey Folks,

This is an odd one...

I have an '86 TPI motor that has a Larrys Electric harness and 1227730 computer (speed density, no polution bits, EGR block off and no 9th injector). The cap/rotor is new, plugs, wires, starter, etc. Also the fuel pump is a Walbro GSL392 - so rail pressure should be good.

It has an old looking Accel 140003 coil on it. Unsure the age of that, as it was on the car.

The motor is sitting in a 1951 Mercury pickup, and when I put in the motor, I purchased 0280-155-771 "19lb" injectors from Cruz'n Performance. They all read 16.4ohms

The truck developed a cold start issue that was sporadic and got worse, and eventually starting it was hit and miss, unless spraying the TB before firing.

I've reset the TPS and the cold start seems great. But once warmed up, it doesn't want to start. It turns over but never fires.

I'm worried that the injectors maybe be the cause and there seems to be some discussion around them being 17lbs.

Sorry for the novel, just trying to be thorough

Thoughts? Injectors and ICM seem fairly common

Thanks!

BaggedMerc

The Temp sensor looks original, so maybe that?

I let the truck cool to 170ish and it fired right back up, so not sure if that's indicative of a temp sensor

PaulyC

Hook a scanner up to it and have a look if you can. Coolant temp sensor is how the cpu knows to enrich when cold. I think sounds like it may be feeding back higher temp than actually exists. You can bench test it also but I don’t have that info with me at the moment.

PaulyC

Reading your first post again, you said you reset the TPS and the cold start was good but now there is a hot start problem. It kind of sounds like two different things but no worries. What are you using to set the TPS? You should have between .46 and .61 volts at closed and right around 5v wot. If that is incorrect you can also have starting issues like the crank no fire you are talking about now. You can do an easy check with noid lights to see if the injectors are even getting a signal when cranking. If they aren’t firing you may have a problem with the tps adjustment. If the feedback voltage is high it thinks you are trying to clear a flood and cuts the injectors. Now that said, this would also apply when the engine is cold so it doesn’t fully explain what you are seeing but maybe it gets you in the ballpark. I wouldnt even consider injector size, if the setup was running before. If you haven’t been running successfully with them maybe, but leaning towards no.

BaggedMerc

Thanks for that!

I'll be bench testing the temp sensor today. EDIT: What a pain in the nuts to try to get to. Maybe I won't test it lol. Basicall check that the ohms decrease as temp rises.

I don't have a noid light, but perhaps the local place that loans out specialty tools may have one.

As for the TPS - I agree, they are probably 2 separate issues, but I figured I'd list it so everyone had the full information .

BaggedMerc

Noid light shows that the injectors fire when it won't start, and fuel pressure when it is running is 58psi.

PaulyC

THats good, so I’m assuming it’s cold during this? Either way, you said the fuel pressure is 58 when running, what is it when cranking? We need good pressure when cranking as well. Does the pump turn on for a couple seconds and pressurize the system when you turn the key to run? If all of that is good we can reasonably assume we are getting fuel. Next check for good spark.

BaggedMerc

This shitty loan a tool pressure gauge started leaking so I didn't get a prime system reading before start. The pump is a GSL392 from Walbro with all new AN6 lines and a inline filter... So that plus the running pressure, I'd say good fuel.

Noid light shows the injectors firing.

Now, for spark, what's the best way to check? I ordered a cheap ICM and water sensor. Easy to replace and cheap. So why not?

PaulyC

Just pull a plug wire and either plug in a known good plug or pull the plug from the cylinder and plug it in to the wire and just make sure the ground strap from the plug is touching the block or something well grounded and in a position you can see it when cranking. Just don't hold it while cranking! That will get your attention for sure.

Is it not starting at all now or just really difficult?

BaggedMerc

Does not start at all when hot, without a shot in the TB.

Ah - I thought you were something more elaborate. The ole hold the plug against ground trick is easy enough. Having owned snowmobiles and dirt bikes, this has saved me before haha. Maybe a tomorrow job.

PaulyC

It sure sounds like a fuel problem if you give it a squirt and it fires. If have a new temp sensor ordered throw it in and hopefully that works. If not I think we still need to verify fuel pressure during cranking because it’s obvious we are not getting enough fuel to light it off. I think your spark will be just fine.

Once it starts with a squirt, does it run fine or stumble around?

BaggedMerc

PaulyC

We’re getting into scanner territory now. We need to see things as cpu sees them. We talked about the tps, I would like to verify the throttle blades are indeed closed and the tps indicates the correct voltage (or resistance, however you want to check but a scanner reading would be best and definite). I would also like to verify the iac is clean and seated as well. It sounds like there is a fuel starvation on startup, that would also mean we need to know that the coolant temp sensor is also reading correct.

Just out of curiosity, next time it won’t fire, see what happens if you hold the throttle wide open. It shouldn’t help but that will help verify we have too little fuel and we aren’t flooding. I think the result will be predictable but that way we know for sure.

amlv20

What does fuel pressure do with key off over an hour or two?also after you turn key off disconnect your vacuum line to fuel pressure regulator at the intake,Keep an eye on it to see if raw fuel comes out,you may need to tip it down a bit to get the fuel out.

PaulyC

Hey Merc, I was just looking over this again and I don't know why I didn't notice this before but the fuel pressure is quite high. You should see 38-46 psi on prime, then idle should be about 8-10psi less. Don't know if that will help your problem but it is too high.

Abubaca

iTrader: (3)

I saw that too as I read through.....58 is extremely high, even at WOT, let alone 50 at idle. I'm at 32 at idle. That's a LOT more fuel in the mix. Literally. Enough to flood? I dunno. Problem or not, you'd wanna fix that.

MrPackstin

iTrader: (9)

Ohm fuel injectors again.