So I have been doing some research on this topic and think I may have pinpointed the issue but I am not sure. I was driving my 87 Gt yesterday and all the sudden my engine started sputtering and then died. I pulled over and tried to start it, it was crank over fine, then start up for a little bit (maybe 3 seconds) then sputter and die. I dont believe it to be electrical since it the car will fire and run for a little while before dying. My guess is that it is the fuel pump? When I start that car I can hear the fuel pump for 2 seconds and then when I start it I get the same thing. Starts, sputters dies. I was not sure if it was a bad fuel pump relay to I tried plugging it into the AC Relay and got the same result.
Is this a sign of a bad fuel pump or something else? Today it ran for 10 seconds then sputtered and died. (By the way the fuel tank is full)
I will go ahead and try that. I will let you know what I find. Any quick tips for checking the fuel pressure?
Its like taking tire pressure but you'll need a fuel pressure gauge that screws on the fuel rail at the schrader valve fitting. You should have around 43 psi. with the key on. if you have fuel pressure then check for spark. The most common problem is usually fuel or spark. Also check for trouble codes.
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So I went to my local harbor freight and picked up a fuel pressure gauge and followed the instructions of a youtube video. Checked the fuel pressure on the schrader valve on the fuel rail.
I recorded what I got with my Fiero, here is a link the the video I just took. Here is a link Here" TARGET=_blank>https://youtu.be/_PYLDGQLg5UHere
As you can see I am getting about 44psi when primed then then it goes to about 38 when the car is running. Just before it dies. Is this okay? Could it be a fuel filter issue?
No, but you might have a leaking injector (or two or more)... and/or the short length of hose inside the gas tank may be starting to rot.
The drop in fuel pressure might not necessarily be the cause of the engine now not starting... unless the plugs are getting soaked from leaking injectors. Pull the three "easy" plugs (for now) and have a look at them. See if they're crudded up.
[This message has been edited by Patrick (edited 04-09-2019).]
I will check back with you guys this Thursday and let you know what I find. If anyone has any other suggestions I’d be happy to try those as well. Just trying to get this figured out so I can take her out this weekend.
Check your injector fuses. There's 2 of them, one for each bank of cylinders. If one of those fuses blew, it could act like what you're experiencing. Sometimes you can run on 3 cylinders, but not very well and every car is a little different.
I agree with Patrick that it doesn't look like a fuel pump problem, but it does look like the pressure drains down quicker than it should when the pump is off. You probably have a leak somewhere (most likely at injectors). It's also somewhat common for fuel to be leaking past a faulty fuel pressure regulator. To test that, disconnect the reference vacuum hose that leads to the manifold, and put suction on it and see if fuel comes out. If you don't have an appropriate tool, then the "not so safe" shortcut is to just suck on it with your mouth. Try not to swallow any gas.
I don't think the leak in your fuel rail is causing it to behave this badly, but it's something to keep in mind to investigate at some point. The worst case would be if it's leaking past injectors enough to soak the plugs though.
There are a few things you can check with a fuel pressure gauge, so I'll give a list here: - When key is turned on, fuel pump should prime for 2 seconds and pressure should hit the low 40s. This means the fuel pump and fuel pump relay basically work (but doesn't prove the pump is keeping up with demand at all times).
- When you bump the starter (don't hold it), fuel pump should prime again for 2 more seconds, just like when you turned on the key. This means the ECM is seeing the distributor reference pulses. If you *hold* the starter, then the oil pressure sensor gets involved and invalidates the test.
- When you start the engine, fuel pressure should maintain a constant differential from the air pressure in the manifold. This is why there's a vacuum hose between the manifold and fuel pressure regulator. It's normal for it to drop into the 30s when idling, this is because of the manifold vacuum. Manifold air pressure is low when idling. By varying throttle, you can make the manifold air pressure increase and fuel pressure should increase along with it. If you want to be really thorough, you can hook up a manifold vacuum gauge alongside the fuel pressure gauge to see that they track with each other. The ECM assumes that the differential between fuel pressure and manifold pressure will remain constant. If this isn't happening, then the ECM can't properly calculate how long to open the injectors.
- When you turn off the engine, fuel pressure should only drain down very slowly. I don't know an exact threshold at which to say there's a problem, but it's normal to leak say 5psi in 15 minutes. That's roughly what I remember seeing on a car with a freshly serviced fuel rail/injectors. 5psi in 10 seconds is too much and indicates a leak somewhere.
The checks with the engine running obviously aren't feasible when it won't idle though.
[This message has been edited by armos (edited 04-10-2019).]
Just got back to working on the car to see whats wrong with her. I currently have the intake manifold off. I already smell fuel. Should I be smelling fuel or does this indicate a leak somewhere? Looking at armos post. When checking the fuel pressure regulator, if I place suction on it and fuel comes out does this indicate my leak? Would this be the reason that my fuel pressure drops so quickly? Thanks again for all the help friends
Originally posted by iboesen: When checking the fuel pressure regulator, if I place suction on it and fuel comes out does this indicate my leak? Would this be the reason that my fuel pressure drops so quickly? Thanks again for all the help friends
So I tried sucking on the fuel pressure regulator and I did not see any fuel come out. I went on to remove the fuel rail and observing the injectors it looks like one of them is "gas-ie" or kind of wet. All around the injector. Are there any other tests that I can perform while I have this off to make sure it is in fact the injectors?
Correct me if I am wrong, but would the fuel pressure drop as fast as it would in my video due to just one injector?
None of these fuel questions would cause a sudden stop in the engine running. So yes, one leaky injector could show a loss of fuel pressure that you have, but it's been that way for a while, and the car was working. If you crank the starter and notice the tach moving up to 300 or so, the primary ignition is working. If the tach does not move, remove the ICM from the base of the distributor and have it tested at an auto parts store. The test is not perfect, but it may tell you something.
If I turn the key to the on position for 3 to 4 seconds, the car will always start, but quickly die. If I try to start right away without giving it time to pressure up it will just cranks and sputters. Which led me down the path of fuel, and the loss of pressure.
The tach has been erratic since i purchased the car several weeks ago. I will go ahead and remove it and take it down to the auto parts store.
Im back everyone, went to Autozone and had them check the ICM. Turns out it was bad! Slapped a new one in there and she runs again! Also after looking at the fuel rail the injector that had the leak was held in by a broken retainer. Purchased a pack of them too, so I guess it was a good thing I took apart the fuel rail after all.
I want to thank everyone who chimed in and helped me with the fiero. I bought it a couple weeks ago so I am sure I will be back with more questions.
...had them check the ICM. Turns out it was bad! Slapped a new one in there and she runs again!
Great, but now the $64,000 question... did you apply the proper heat sink compound between the ICM and the base of the distributor? The clearish "grease" that is sometimes supplied is useless. It needs to be the pasty (usually white) stuff, same as is used under a computer's CPU.
If I try to start right away without giving it time to pressure up it will just cranks and sputters. Which led me down the path of fuel, and the loss of pressure.
The path was temperature, and not fuel pressure....The ICM gets hot and fails, then you gave it time to cool off and work again.
edit: if the grease was white...it's OK.
[This message has been edited by Gall757 (edited 04-14-2019).]
Yes on carry a spare ICM....Most of them fail quickly...Get the AC/Delco ICM- they last longer.....but keep the other as a limp-home spare......You can buy some really good heatsink grease on Amazon..."Arctic silver" in a 3.5 G mini tube. Also, carry........the tools to change the ICM would be a necessity.....
The choice of thermal compound might be splitting hairs, but I think Arctic Silver "Ceramique" is a good choice. According to notes, I've had it on my ICM since 2013. Beyond that, any reputable brand of white thermal paste is probably fine. What are reputable brands? Honestly I'm not up to date on that. Arctic Silver is an old favorite going back to the 90s-00s. Whatever you use, keep in mind you just want a thin layer of the stuff, don't overdo it.
Arctic Silver Ceramique seems to hold up well for years in PCs that I've worked on. Sometimes cheap no-name stuff can be more prone to dry out and get chalky, at which point it doesn't transfer heat well anymore.
This is a more demanding application than a PC. We're leaving it there for an indefinite number of years, and it's going to sit in the weather, see varying humidity, and routinely get both colder and hotter than a CPU ever gets. Our goals are also a bit different than PC gamers - we're not trying to shave fractions of a degree off the temperature, we're trying to have it work "good enough" for a very long time in widely varying conditions.
I remember looking into "Arctic Silver 5" or whatever it's called, which is the more premium product they sell, silver in color. I decided against that version because there was some data on their web site saying it wasn't rated for as wide of a temperature range, or maybe wasn't as good at filling gaps in rough surfaces.. can't remember which. I've disassembled lots of old PCs, and whenever I encounter silver colored CPU paste, it has always been dried out and chalky. This has made me generally skeptical about the service life of silver paste. At least for our purposes, I think "Ceramique" is the more suitable product.
I wouldn't break my neck trying to find it locally, but last I knew Arctic Silver Ceramique was sold at Fry's Electronics (in the area where they sell CPU heatsinks), and at Radio Shack (if those exist anymore). Other than that, local PC repair shops might have it, unless they're using generic stuff on the PCs they service. Maybe Best Buy would have it, and then there's the internet (Amazon, NewEgg). And really, the white paste your ICM came with might be fine. It's just an unknown is all.
Some cars eat ICMs, so I agree with earlier suggestions to carry a spare. If this turns out to be the car's habit, then you don't want to get stranded.
