exercion Posted February 1, 2022 Share Posted February 1, 2022 1988 GL SPFI 5spd. Having the issue that when it's cold, even subzero cold the car starts fine. However, after a drive, if I shut it off, it doesn't want to start. If it sits long enough, it does start up as normal. I searched the forum and read about testing the ohms in the temp sensor and it seemed to be fine (Good resistance cold, dropping hen the car is warm). Contacts were clean, but I cleaned anyway. Not sure my next step. Thinking I should try to get it to do it (I haven't gotten a solid pattern on just how warm and how long to create the issue) and then measure resistance. Next play could be replace the sensor. Not sure. Thoughts? Eric Link to comment Share on other sites More sharing options...
DaveT Posted February 2, 2022 Share Posted February 2, 2022 search for my threads with lots of ohms / volts / temps. See if it tracks more or less. What I would do - tap the wire at the ECU, connect a volt meter, and take a drive, take notes, take temps if you have a way to do it. I have an infrared thermometer, which is really handy for this kind of thing. The volt readings should be smooth changes, not jumping around. It is possible for one of the wires or connections to be broken or intermittent between the sensor and the ECU. 1 Link to comment Share on other sites More sharing options...
exercion Posted February 3, 2022 Author Share Posted February 3, 2022 On 2/1/2022 at 10:58 PM, DaveT said: search for my threads with lots of ohms / volts / temps. See if it tracks more or less. What I would do - tap the wire at the ECU, connect a volt meter, and take a drive, take notes, take temps if you have a way to do it. I have an infrared thermometer, which is really handy for this kind of thing. The volt readings should be smooth changes, not jumping around. It is possible for one of the wires or connections to be broken or intermittent between the sensor and the ECU. Hi Dave, thanks for the reply. Those are the threads I used to learn about testing the sensor. It was about 15F when I checked cold, and if memory serves I was approx 5K ohms. Started it up, warmed to approx 160 (based on the current 160 thermostat, going to switch to a warmer one) and had 500 ohms. Which seemed to follow the correct pattern. Hope you don't mind a dumb question, but where is the ecu, and do you know the pinout? I have two manuals but not access to either at the moment. Eric Link to comment Share on other sites More sharing options...
DaveT Posted February 4, 2022 Share Posted February 4, 2022 The ECU is bolted to the steering column. There is a plastic panel covering it, unless someone removed it. I remove those the first time I do anything under there, have never put one back. Yes, the pinout is in the Factory Service Manual. There is no substitute for the FSM. There may be a link or an online copy somewhere... I can look it up tomorrow, and scan a page. I have a 1986 FSM and a 1990 FSM. The cars are very similar, so either one, or in between would be very useful. There are occasionally a few small differences. Yes, 160 is a little too cool. I have a 180 in one, and the normal 190 in another. Link to comment Share on other sites More sharing options...
6 Star Posted February 4, 2022 Share Posted February 4, 2022 10 hours ago, DaveT said: The ECU is bolted to the steering column. There is a plastic panel covering it, unless someone removed it. I remove those the first time I do anything under there, have never put one back. Ya know those Plastic Covers keep both the 4 and the 2 Legged Rats out, if only to delay their progress... Link to comment Share on other sites More sharing options...
el_freddo Posted February 5, 2022 Share Posted February 5, 2022 On 2/5/2022 at 3:19 AM, 6 Star said: Ya know those Plastic Covers keep both the 4 and the 2 Legged Rats out, if only to delay their progress... They also help keep your legs out of things that would severely damage them in a crash, not hugely, but it would help to some degree! Plus it looks better than looking at the wiring nest that can be under there some times... Cheers Bennie Link to comment Share on other sites More sharing options...
exercion Posted March 17, 2022 Author Share Posted March 17, 2022 Following up with this, it's more than simply not wanting to restart after running. While trying to nail this down, I found this out: It starts and runs beautifully in the morning/evening/anytime it's been sitting for hours. Idles high til it warms up, then drops the idle to normal rpm's Purrs like the proverbial kitten, no missing, sputtering, throttle needed, etc. 25 minutes after start-up, almost enough to set your watch by, it bucks stutters, sounds like an old carbed engine loading up, pops a bit, then shuts off. Will not restart for at least an hour and a half, two is better. Even then it hesitates to actually light off. Let it sit a few hours, and it's back to hit the key and boom, starts right up. No vacuum leaks external (sprayed starting fluid at all vacuum connections), idles at 21-22" vacuum. EGR valve is stuck in whatever position it is in (guessing closed since it's holding good vacuum, and I took the valve off to see if it needed cleaned etc. and it seems closed). I have not checked fuel pressure yet, have a gauge coming, but the fact that it is so predictable as far as when it happens makes me doubt that, but I'll check. Also, I can drive it, no loss of power, climbs the mountain well, as long as I don't turn it off. Changed spark plugs (they were due) no bad signs there. Checked resistance on the coil, it was in spec, but one of the screws had bad threads, so I changed that. Same issue. Tested volts and resistance on CTS, in spec. Had another so I tested it, in spec. Installed, same issue. On the chance that it still was a temp issue causing the no-restart thing, when I had it in that mode I plugged in the cool CTS, so it would maybe think it was cooler and adjust to allow a start. Didn't work. Only codes flashing are 34 & 35 EGR and purge, as noted the EGR is stuck, and I have my vacuum gauge plugged into the line that goes to the canister. No other stored codes in either read memory or D-check. Pretty baffled here. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted March 17, 2022 Share Posted March 17, 2022 (edited) pardon my ignorance but, does the car have a mechanical or underhood fuel pump? I ask because it seems like vapor lock to me. I had an old '78 Honda Civic that started doing this when alcohol was first added to fuel. I had to carry a gallon jug of water with me to douse the FP under certain combinations of short shut-downs after fully warmed-up. Edited March 17, 2022 by 1 Lucky Texan Link to comment Share on other sites More sharing options...
idosubaru Posted March 17, 2022 Share Posted March 17, 2022 5 hours ago, 1 Lucky Texan said: pardon my ignorance but, does the car have a mechanical or underhood fuel pump? I ask because it seems like vapor lock to me. I had an old '78 Honda Civic that started doing this when alcohol was first added to fuel. I had to carry a gallon jug of water with me to douse the FP under certain combinations of short shut-downs after fully warmed-up. Wow! how did you figure out to use water?!? These have electrical fuel pumps in the back. Fuel is a good place to check. Check fuel pressure when it stops running. 1. how long has it been running and driving? 2. has it recently sat for a long period of time? Link to comment Share on other sites More sharing options...
exercion Posted March 17, 2022 Author Share Posted March 17, 2022 2 hours ago, idosubaru said: Wow! how did you figure out to use water?!? These have electrical fuel pumps in the back. Fuel is a good place to check. Check fuel pressure when it stops running. 1. how long has it been running and driving? 2. has it recently sat for a long period of time? Up til this little episode my Subie has been my daily driver, 40 miles round trip to work 5 days a week, plus assorted running around. Link to comment Share on other sites More sharing options...
idosubaru Posted March 17, 2022 Share Posted March 17, 2022 5 hours ago, exercion said: Up til this little episode my Subie has been my daily driver, 40 miles round trip to work 5 days a week, plus assorted running around. Okay, I'd check the fuel supply - check pressure if you can. If you can't check pressure, wait until it doesn't start and pull the main fuel supply hose in the engine bay and have someone turn the key while you watch how much fuel comes out out of the hose. Just need to watch it for like 2 seconds or less so we aren't talking much fuel. Catch it in a cup or in an emergency I've just run it right down the side of the frame rail carefully. It should flow out consistently, not dribble out. Link to comment Share on other sites More sharing options...
DaveT Posted March 17, 2022 Share Posted March 17, 2022 T in a fuel pressure gauge, after the under hood filter. It should be 21psi. Significantly less will cause it to run really bad, starving for fuel. One of mine had the pressure regulator fail. Link to comment Share on other sites More sharing options...
exercion Posted March 17, 2022 Author Share Posted March 17, 2022 1 hour ago, DaveT said: T in a fuel pressure gauge, after the under hood filter. It should be 21psi. Significantly less will cause it to run really bad, starving for fuel. One of mine had the pressure regulator fail. I should have a pressure gauge in today or tomorrow 1 Link to comment Share on other sites More sharing options...
idosubaru Posted March 18, 2022 Share Posted March 18, 2022 other possibilities: Bad ECU - got a spare you can swap in? Bad sensor - ive seen O2,MAF, TPS cause issues without throwing a code. Bad wiring. I’ve fixed two with bad wiring. One had starting issues often - I massaged all the intake manifold wiring and found a bad spot where the wiring starts curving down from the TPS. I would just massage while it’s running or go over it abs keep trying to restart. Eventually messing with that one small area would lead to changes. Spliced in a used TPS connector with 6” of wiring on it. Fixed it. The other I couldn’t figure out but fixed it by swapping an entire intake manifold so I assume it was a sensor or wiring. Link to comment Share on other sites More sharing options...
idosubaru Posted March 18, 2022 Share Posted March 18, 2022 7 hours ago, exercion said: I should have a pressure gauge in today or tomorrow Some people shoot in starting fluid or carb cleaner in the throttle body as a test that doesn’t require a gauge. If car starts for like 1-3 seconds then you know it’s not getting fuel. 2 Link to comment Share on other sites More sharing options...
Ionstorm66 Posted March 18, 2022 Share Posted March 18, 2022 Which coolant sensor are you checking? There is 2 wire for the ECU and a 1 wire for the gauge. Make sure you're checking the 2 wire sensor. 1 Link to comment Share on other sites More sharing options...
el_freddo Posted March 19, 2022 Share Posted March 19, 2022 The 20 minute thing to me sounds like something electrical is getting hot then not doing it’s job until it’s cooled off again. Check your coil to make sure it’s giving spark when the issue arises. If that’s not giving spark and a known good one is doing the same then the issue could be dizzy related (would be a very rare occurrence), my thoughts are some sort of electric ignition control module that sends a spark pulse to the coil for the high voltage spark to the plugs. It shouldn’t be to hard to work out if you have spark or not when you have a no start once up to operating temp. Cheers Bennie Link to comment Share on other sites More sharing options...
exercion Posted April 17, 2022 Author Share Posted April 17, 2022 On 3/17/2022 at 3:50 PM, DaveT said: T in a fuel pressure gauge, after the under hood filter. It should be 21psi. Significantly less will cause it to run really bad, starving for fuel. One of mine had the pressure regulator fail. I finally got a pressure gauge in, between other life issues, work etc. According to the gauge, it runs at 23psi, and this doesn't waver when it goes through its bucking shut-off phase. Link to comment Share on other sites More sharing options...
Steptoe's photos Posted April 24, 2022 Share Posted April 24, 2022 only 21 psi ? OK , I was thinking 36psi but that is for mpfi and their turbo options. I would think you need to test the pressure when it won't restart or plays up, before it gets a chance to cool down and drive normal Link to comment Share on other sites More sharing options...
exercion Posted April 24, 2022 Author Share Posted April 24, 2022 9 hours ago, Steptoe's photos said: only 21 psi ? OK , I was thinking 36psi but that is for mpfi and their turbo options. I would think you need to test the pressure when it won't restart or plays up, before it gets a chance to cool down and drive normal I already did that, it holds the same fuel pressure when it successfully starts, when it goes through its shutdown phase, and when it refuses to start. 1 Link to comment Share on other sites More sharing options...
el_freddo Posted April 25, 2022 Share Posted April 25, 2022 When it refuses to start, do you have voltage where it needs to be? Eg: at the ECU power wires, ignition coil, do you get spark when turning it over when hot and not wanting to run? If you have spark does it try to fire up with some start ya bastard or aero start sprayed down the intake? Cheers Bennie 1 Link to comment Share on other sites More sharing options...
Craigar Posted May 11, 2022 Share Posted May 11, 2022 I'm in a state of serious *suspense* waiting for the outcome to this chase scene (or conundrum)? Link to comment Share on other sites More sharing options...
Craigar Posted January 16, 2023 Share Posted January 16, 2023 meanwhile, back at the ranch... Link to comment Share on other sites More sharing options...
azdave Posted January 16, 2023 Share Posted January 16, 2023 Just one more online repair thread for someone to discover in a search and read completely to the end only to find out it was never resolved. OP has not posted since last April so I think we can put a fork in this one. Link to comment Share on other sites More sharing options...
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