Hello all my name is: chris
I have a: 94 3000gt SL
It has the following issue: so my car will start and runs for about 10 minutes and then dies and won’t start back up for a while. I’ve replaced the fuel pump, fuel filter, spark plugs, cleaned the fuel injectors out and replaced the o-rings on them. I even got a 2nd ecu to see if that was the issue and it is doing the same thing. I had my fuel pump wired to a toggle switch and it would run for about a hour tops then die. Any help as to what it could be would be appreciated
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I’m going to throw a wild guess out there are guess you hear a relay click right before it shuts off.
If you do then your MFI relay behind the passenger console cover is the likely cause.
Other possible causes though would include the PTU/igniter.
You’re going to need to do some actual diagnosis to go in the right direction. Instead of chucking parts at it like you’ve been doing you need to figure out what’s missing to let it start back up. Fuel, spark, air, timing are necessary for a car to run. If fuel is missing look at the MFI. If spark is missing look at the PTU.
I’ll have to check the ptu because I have a new mfi relay as well. I was told back a couple months ago it was most likely fuel so I started there with a new pump, relay, and cleaning the injectors along with putting new o-rings on.
I just also guess, but sometimes the cause of the issues are much common and less complicated practical one, so I just can tell you an another possibility as a “root cause”, even if maybe it occures not too often.
I dont know what kind of battery you use.
In some kinds of those where “gel” is loaded inside instead of liquid, sometimes there will be some so small micro cracks which simply cannot be seen when the car starts to run, but when the engine start to work, then because of the radiated heat those cracks can be growing temporarly until it gets the heat from the running engine. Then it can be even at this point hard to see, but in the same time sometimes it grows enough to cause separating in the gel blocks, and of course then the accumlator/battery doesnt functional as normal which leads electric anomalies or disfunctions, insufficent power. Of course until the crack just increasing in size but doesnt reaches a critical size and doesnt separates the parts enough, the engine can run without any experienced issues. It is not sure of course that this the matter in your case also, but there is a possibility maybe. And it is hard to detect, as when the car stops because of the failing battery and electrical part, then the battery cools down, and the crack will be shrunked back to its original lesser size, and at that condition it is working as normal again. …working until the cycle repeatedly starts again with the received heat.
So in long story short it is maybe also worth to try to use and test the car with a new battery!
I am sorry if it wont work, but there is a slight chance, and if thats it, than it was easy to eliminate, it worth a shot! I assume you can even borrow/lend a battery for just a little time for testing from someone close to you, its not even must to buy just for that!
I’m sorry for my very poor english, as “cracks” I mean the thing which is looks like a thin line when something starts to break, or it is not broken, but damaged with this “line”. Like when bones dont completely brake, just getting damaged this way… Maybe the “fracture” is the proper word for that.
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You were told it was most likely fuel, but you didn’t actually do any tests. This is why diagnosis is so important. You’ve thrown a ton of money at the car and it’s still doing the exact same thing.
I’ve literally spent 8 hours diagnosing a random stall and no start before on a 93 Civic. I quickly figured out it was a fuel issue, but I could only “trick” the car into starting, but it wasn’t a fix. Lots of time and in the end we found out there was an ECU issue. The only money spent was replacing the ECU. No money wasted on fuel pump, or filter, or injectors, or plugs, or wires because we didn’t shotgun parts at it.
The point is, take your time, do it right, and save yourself money.
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As stealhee just said, spending time on testing and diagnostics for the long waited result is always an unpreferred part of the procedure, but it ismuch worth itand the only one which requires no money and can prevent unneccesary expenses, waisted money. ^^
Additional to that, even if a test doesn’t reveals the source of the issue, at least it shows that there is no problem at that part which is also good and relaxing to know, or it can reveal other things, so it is never a bad thing to do, and usually even if it has a cost, still thats much cheaper at the end than just guessing or tying to fix an issue with buying and replacing parts based only with pure probabilities! 
Yea I’m done throwing money at things with this car without being sure that’s what’s wrong with it. Battery was replaces due to having a bad cell. That I tested and made sure was bad. As far as the other things I didn’t test when I should have
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Have you tried letting the dealer diagnose it for you ? Anytime my car has a problem I just let them diagnose it to save me the hassle of trying to figure out whats wrong.
No I haven’t closest mitsubishi dealership to me is a hour away and my car won’t be able to make that drive and I don’t have access to tow it without having to pay a company to do it which around here will cost me over $300 just to have it towed there
Sounds like the change you made to running the fuel pump made a difference. I’d look to monitor the fuel pressure [gauge] or at least see if the pump still runs when the car shuts off.
So I wired the fuel pump back to the stock wiring from the toggle switch and it still does the same thing. It would be off when I shut the toggle switch off when it was wired to that. I seemed to have made progress from when I got the car back back in October when it wasn’t running at all.
Crank Angle Position Sensor