Tehnation Posted November 11, 2021 Share Posted November 11, 2021 So I am trying to track down an issue. Car starts and runs when cold for like 5-10 minutes, but when it gets warm or hot it dies and won't start until it cools down again. Also doesn't cause any CEL's. I've changed maf, fpr, fuel pump, alternator, and fpcm, and added a 4 gauge ground strap to engine harness. Thought it might be injectors, coil packs or spark plugs, but all of them failing at the same time and giving no CEL? My ECU has a fried fan circuit, but it was working fine, the main fan is just always on. Something is getting hot and the car dies like it ran out of gas. I thought it might be old fuel, its a mix of 1 and 2 year old gas atm, but it would run like crap as well. I have a used ecu that I need to clone with my current ecu. But I am not hopeful that will solve the issue, a bricked ecu wouldn't cause these kind of symptoms. Also going to push air through fuel lines to see if anythings in there, but I doubt it, it wouldn't start. Thought maybe fuel filter, but like a clog it wouldn't start and run for 5-10 minutes then just die. I don't think. Can anyone solve this riddle!? I'll even give an amazon gift card to the person who comes up with the answer! Link to comment Share on other sites More sharing options...
devobuzz Posted November 11, 2021 Share Posted November 11, 2021 My guess would be fuel pump. Can you monitor the fuel pressure while it's running to see if it drops? Link to comment Share on other sites More sharing options...
Tehnation Posted November 11, 2021 Author Share Posted November 11, 2021 Fuel pump, no, fuel pump housing... maybe. The fuel pressure is where it's supposed to be, I have an inline gauge so I can see that the system has pressure. I would have to keep an eye on the gauge and watch until it dies to see whats happening at that exact moment, and or log some data. I've pulled the fuel pump out like 4 times already, and now I have 2 functioning pumps. If it were the pump or housing it wouldn't be so consistent, like why would it only fail after 5-10 minutes, and do the same thing for 2 pumps. If it were the housing it would just fail, unless the fuel filter is bad. A bad fuel filter would have bad idle as well. It starts fine, warms up fine and idles fine. Link to comment Share on other sites More sharing options...
devobuzz Posted November 12, 2021 Share Posted November 12, 2021 Sorry I do not have much troubleshooting experience with these cars as mine has not had major issues since I bought it in 2004. <knock on wood>. I do have years of experience with my other cars though. Is there a fuel pump relay? Perhaps the contacts in the relay are bad? Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 (edited) Don't worry about it! I'm just out of the usual answers. So before I go crazy and just start replacing everything, I am just looking for any ideas at this point! You only have the info from the original post so I can't expect you to know everything I have done. But I will try swapping the fuel pump relay! Not a bad idea! I think its under the hood, there should be a relay and a fuse. Edited November 12, 2021 by Tehnation Link to comment Share on other sites More sharing options...
Pleides Posted November 12, 2021 Share Posted November 12, 2021 When my sidefeed injectors started leaking, hot starts became much more difficult. This was right after an engine rebuild and I didn’t replace my o-rings on those, so they probably started leaking shortly after the engine was put back together. Alternatively, have you disconnected the battery after the car dies and then reconnected it to make sure this isn’t a learned issue from the car? Perhaps a CEL will come on if you do this? Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 I didn't replace my o rings on this rebuild, but they do have less than 500 miles on them. This car spends most of its days pulled apart, and when I dismantled the motor I kept the entire intake manifold and wiring harness in one piece so the injectors never moved. Wouldn't I smell gas? I have top feeds so a leak is more noticeable. I do like the idea of resetting the ecu to see if its a learned issue! Link to comment Share on other sites More sharing options...
Infosecdad Posted November 12, 2021 Share Posted November 12, 2021 So if you start it and it warms up, the next time it won't start. What does it do exactly when it "won't start"? Also, what do you have to do to get it to start again? Is it a reset or just wait until cold? Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 I'm not sure if its time or temperature that I am waiting on. When its cold or gets enough time to rest it will start and run exactly like it should. After some time it will just die and then it wont start. It cranks and has fuel pressure but won't start like it has no fuel or spark. I leave it alone for a while and it will start again, then rinse and repeat. It seems the colder it is the longer it runs in its 5-10 minute window. I'm also going to try adding an extra grounding wire to the battery. Link to comment Share on other sites More sharing options...
Infosecdad Posted November 12, 2021 Share Posted November 12, 2021 That can still be the ECU or a related electrical component. Once it gets too warm, something expands and it fails until it cools off and contracts again. I've seen this with a broken solder joint, connected when cold, expands and separates when hot. I think the FPR and pump are still worth it, you now have good, stable fuel pressure. Link to comment Share on other sites More sharing options...
Max Capacity Posted November 12, 2021 Share Posted November 12, 2021 FWIW, for those that have not been following, here is his thread, https://legacygt.com/forums/showthread.php/tehnations-ballin-budget-rebuild-250013p25.html 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 I was thinking something electrical as well but what would fail and not cause a CEL? That's what's making this such a pita, I can't get a CEL to point me in the right direction. Maybe a relay? I don't think there is one for anything fuel/spark related though. I have to go get a new fan relay before I install the new ecu, don't want to blow another one up. Going to work on the ecu today. I also added a ground to the battery, seems like one of the wires is in bad shape, melted plastic around the wire. Probably from the starter. Link to comment Share on other sites More sharing options...
Infosecdad Posted November 12, 2021 Share Posted November 12, 2021 I was thinking something electrical as well but what would fail and not cause a CEL? That's what's making this such a pita, I can't get a CEL to point me in the right direction. Maybe a relay? I don't think there is one for anything fuel/spark related though. I have to go get a new fan relay before I install the new ecu, don't want to blow another one up. Going to work on the ecu today. I also added a ground to the battery, seems like one of the wires is in bad shape, melted plastic around the wire. Probably from the starter. In my experience and research, when an ECU is dying, there are no CELs. CELs only trigger for specifically coded events, voltage on sensor out of range and such. There are many things that can happen that someone didn't think or know to write a CEL for. I suspect after it gets hot the computer is not sending the spark signal. You have air and fuel, so in my mind it's spark that's missing when hot. I thought maybe coil, but that would be rough 3/4 firing, not dead. So I trace back what can kill all four coils, and there isn't much that I know of other than the ECU control. I would try to get a spare ECU setup to test to know if that's it. Kinda hoping it is, because if it's not the ECU, it's gonna be a bear to track down. Link to comment Share on other sites More sharing options...
xt2005bonbon Posted November 12, 2021 Share Posted November 12, 2021 Do you have BtSsm or romraider? How are your fuel trims? Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 (edited) Did a log on my accessport. Only have the AP. datalog4.csv Edited November 12, 2021 by Tehnation Link to comment Share on other sites More sharing options...
xt2005bonbon Posted November 12, 2021 Share Posted November 12, 2021 (edited) Looks like you have a massive vacuum leak somewhere. I can see as the coolant temp is increasing (engine warmed up), it begins to do fuel correct and latter on keeps adding fuel. Then your idle fuel learn is pegged at the max +15%. That's a lot. Edited November 12, 2021 by xt2005bonbon Link to comment Share on other sites More sharing options...
xt2005bonbon Posted November 12, 2021 Share Posted November 12, 2021 Also, you need to log the OCV (or VVT) L and R to make sure they are in sync. And don't reset the ECU so it does not have to keep relearning. Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 I think I cloned the ecu right... who knows, but I forgot to unmarry the AP..... gotta do things twice... Vacuum leak hmmm..... massive??? I'll smoke test it tomorrow when its not raining. Link to comment Share on other sites More sharing options...
xt2005bonbon Posted November 12, 2021 Share Posted November 12, 2021 Well, 'massive' is a strong term I guess . But it should be a pretty obvious one I think. Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 (edited) Just did a smoke test, only see smoke coming out the intake. If there is one, its not that big. I guess once I can get it to start again, I'll start spraying some brake cleaner to see if there are any leaks under vacuum. Wondering if this evap purge valve is the reason for the vacuum leak. Makes that accordian noise sometimes, its very faint though. This is a picture from another thread, mine is fairly new though. Edited November 12, 2021 by Tehnation Link to comment Share on other sites More sharing options...
Max Capacity Posted November 12, 2021 Share Posted November 12, 2021 Can you post a photo of your smoke machine ? Was the smoke coming out in one spot on the intake or every where ? Did you plug the air feed hose off the air filter box past the MAF ? I have used a pint size paint can to plug that hose. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 It was coming out the air filter. I have a grimmspeed. Didn't cap it off though.... probably should have done that to add some pressure to the system. Will try again. Got it a while back off amazon for like 100 and change. Works well, just needs mineral oil. Requires an air compressor. Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 I plugged the intake, no smoke. When I first got the car I was chasing a vacuum leak for years, so I am ocd with all the connections. I don't think there is a leak. Link to comment Share on other sites More sharing options...
Max Capacity Posted November 12, 2021 Share Posted November 12, 2021 Thanks, that looks doable. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Tehnation Posted November 12, 2021 Author Share Posted November 12, 2021 https://www.amazon.com/gp/product/B0746SL9D6 That's what I bought, 120 bucks. Figured why pay someone 100 bucks or so to test when I can buy a machine and do it myself whenever. Link to comment Share on other sites More sharing options...
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