Stuck injector?

KevinB

Well-Known Member
Joined
Dec 2, 2004
I got a GN here I'm working on. It will not build fuel pressure. What I know it's not so far:
1. fuel pump...has double pumper. Jumping second pump does not solve issue.
2. regulator. replaced with known good one.
3. gauge. checked with two gauges...one of which is known good.

Car has a dead cylinder. Not a spark issue. Checked that. Has injector pulse at that cylinder. Plug gets very wet even with harness disconnected from that injector. Car is an '85 with an '87 conversion. I did notice they forgot to plumb in a fuel filter.

Fuel pressure only goes to 20psi or so with the pump running and car off....no matter how much regulator is cranked down. Will a stuck injector (80lb injectors) cause that much of a fuel pressure issue? Pressure goes to zero instantly when pump is shut off. It also takes it a few seconds to get to 20psi when pump is fired up.
 
I got a set of injectors here (not for his setup). I'm thinking of throwing those in here to see what happens. Problem is that this car has a stock modded ecm. The injectors in it are low imp injectors. Will running high imp injectors on a modded ecm hurt it? I don't think so...but maybe one of you out there knows the answer.
 
I got a set of injectors here (not for his setup). I'm thinking of throwing those in here to see what happens. Problem is that this car has a stock modded ecm. The injectors in it are low imp injectors. Will running high imp injectors on a modded ecm hurt it? I don't think so...but maybe one of you out there knows the answer.

When i had my ecm modded to run low impedance injectors it came with a sticker attached saying that the ecm was now compatible to be used with both low and high impedance injectors.

To find out whether or not it's a stuck open injector wouldn't it be all that's needed is to replace the injectors with some known good ones and then check the pressure to see if it holds, i don't think you would really need to run the engine unless you have the chip for those injectors.

If it is a stuck injector you could send them to Chuck Leeper and he can fix them up for you. :smile:
 
Did you drop the tank? Check to make sure the rubber lines are tight in the tank on the pump(s). Not all line is fuel submersible, they can rot out in the tank. I also had a stuck injector before and the car ran, plenty of pressure.
 
Did you drop the tank? Check to make sure the rubber lines are tight in the tank on the pump(s). Not all line is fuel submersible, they can rot out in the tank. I also had a stuck injector before and the car ran, plenty of pressure.

I have seen where stuck open injector made a dead miss but not to the point that fuel pressure can not build.

I have to go with the above post and check the hoses in the tank.

You may have a couple gremlins in there.
 
It could be more than one injector stuck open.

I would do the easiest check first and that would be to swap out the injectors before dropping the fuel tank. :smile:
 
I was thinking about the double pumper connection last night. Looks like I have a few thongs to check out. The car sat for 5 years so anything is possible.
 
From personal experience with a stuck injector- a giant puddle of fuel will be coming out the exhaust and will tell you of any leaks on the downpipe too :eek: The busted rubber hose in the tank is also from personal experience when I bought my unrunning GN and it had the exact symptoms you describe, build psi but will start and then not run- 20psi max FP. Other ideas when I had that was the fuel lines were clogged.
 
Kevin

Would you have any way to cap off the fuel line @ the rail--dead head it. Might be easier than removing inj. Don't know if holding your finger over the end would work or not.
 
Oh yeah....this car is leaving a puddle behind the tail pipe.

1. Send injectors to Chuck Leeper for cleaning, no fuel filter = clogged injectors for sure.

2. Drop tank and make sure the pumps are hooked up correctly with new hoses, clamps and filter sock.
 
I think I hear a huge leak in the tank. Pulling it here in a few minutes. Prob send injectors out too. Car seems to have numerous issues:eek:
 
Fuel pressure issue found:)
 

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Looks like someone jb welded it. Hanger was pretty much junk. Replaced it with a stock hanger and single pump. Car should be a mid 10 sec car. One pump and alchy should be enough.

Now the pressure does not bleed off. Still got a dead hole. Have injector pulse, spark, compression and a wet plug. Hmmmmmmmm....
I know it's that cylinder. Unpluging every other injector while the car is running...the car stumbles. Number one does not change.
 
Just put a fresh plug in and ran the car for 60 seconds. plug was dry and showed no signs of combustion. I'm thinking bad/clogged injector.
 
I would send out injectors and have them cleaned . It might have been a stuck injector that let loose and started working.I had a car with 60lb injectors that sat for two years and car would not start. so I got the car sent to me. I had my buddy crank the engine over while I tapped on injectors and they started working.You can use a low amp probe and current ramp injectors to see if there is a pintle bump in ramp. No pintle bump tells you injector is stuck. You dont want injectors partially clogged at 22psi at wot:eek: Linder is in Indy. injector guru.com or linder tech.com.
 
I would send out injectors and have them cleaned . It might have been a stuck injector that let loose and started working.I had a car with 60lb injectors that sat for two years and car would not start. so I got the car sent to me. I had my buddy crank the engine over while I tapped on injectors and they started working.You can use a low amp probe and current ramp injectors to see if there is a pintle bump in ramp. No pintle bump tells you injector is stuck. You dont want injectors partially clogged at 22psi at wot:eek: Linder is in Indy. injector guru.com or linder tech.com.

I replaced the suspect injector. We're probably going to go with a different set anyways. The ecm that fried was a modded one. Right now it's got a stock ecm in it with low imp injectors. We got to replace one or the other before the low imp injectors wipe out the stock unmodded ecm
 
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