g3nesis Posted December 17, 2011 Share Posted December 17, 2011 Recently rebuilt my 82 l28e with dished pistons new crank new rods/pistons/gaskets/seals stock intake and exhaust, put it in an 79 body and can not get it to run consistent. Had to swap out bad tank and fuel pump. Fuel pressure good, timing set at 20degrees, getting strong spark. It will run great for 2mins(900rpm idle) and then run like a dog. Changed fuel rail thought it may of gotten dirty, compression test results in120/130/135/135/130/130. Now I can't get it to even start with start fluid. Any ideas? Also have a p90a head on it but can not find the wiring to hook up the head sensor. Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 17, 2011 Share Posted December 17, 2011 You need the "head sensor", AKA CHTS. Without it, it will run rich all the time. Good when cold, bad when warm. Flooded probably when it dies. I forgot to connect a water temperature sensor recently and that's exactly what the engine did. Ran good, ran bad, died, fouled plugs. Does it smell gassy? I would pull the plugs, see how fouled they are, clean them up, get the CHTS connected and try again. One problem you might have even after you get it running is poor running and low power due to low compression ratio. The P90 head with the typical dished pistons will give ~7.4 CR. Good for turbos, but your ECU is probably tuned for CR in the mid to high 8s. Quote Link to comment Share on other sites More sharing options...
MadMaxDallas Posted December 17, 2011 Share Posted December 17, 2011 (edited) Actually after reviewing the schematics, there is no CHTS in the 79. Could it be possible they are using the water temp? (I am his dad working on it). As far as dished pistons. Injection volume is based off of the MAF sensor. Since their dished the compression is lower, but the actual air volume is higher. So With some tweaking of the AFM this can be adjusted out. I have a 81 turbo, and put in larger injectors and was able to adjust it down to what it needed to be by adjusting the AFM. In addition, the engine that came out of the 79 which was the original had dished pistons.. Edited December 17, 2011 by MadMaxDallas Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted December 17, 2011 Share Posted December 17, 2011 are you reusing the 79 head? it should be an N47 and the CR should be stock. Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 17, 2011 Share Posted December 17, 2011 Actually after reviewing the schematics, there is no CHTS in the 79. Could it be possible they are using the water temp? (I am his dad working on it). As far as dished pistons. Injection volume is based off of the MAF sensor. Since their dished the compression is lower, but the actual air volume is higher. So With some tweeking of the AFM this can be adjusted out. I have a 81 turbo, and put in larger injectors and was able to adjust it down to what it needed to be by adjusting the AFM. BluDestiny, the first post,last sentence, says they're using the P90 head. The resistance v. temperature curves are the same (they're both shown in the FSMs), they just moved the location of the sensor from the thermostat housing to the cylinder head (apparently after 1979). Your 79 wiring has the sensor plug up by the thermostat housing, the 82 wiring has the sensor plug between cylinders 5 and 6 above the starter. You can either extend the wiring or install a coolant temperature sensor in the thermostat housing. Tweaking the AFM is possible, I'm sure. I was just pointing out that your engine doesn't match what the ECU and control components are designed for. Why did you replace the N47 head with the P90? Just curious, nothing wrong with a Frankenmotor if that's all you have available. Quote Link to comment Share on other sites More sharing options...
MadMaxDallas Posted December 18, 2011 Share Posted December 18, 2011 BluDestiny, the first post,last sentence, says they're using the P90 head. The resistance v. temperature curves are the same (they're both shown in the FSMs), they just moved the location of the sensor from the thermostat housing to the cylinder head (apparently after 1979). Your 79 wiring has the sensor plug up by the thermostat housing, the 82 wiring has the sensor plug between cylinders 5 and 6 above the starter. You can either extend the wiring or install a coolant temperature sensor in the thermostat housing. Tweaking the AFM is possible, I'm sure. I was just pointing out that your engine doesn't match what the ECU and control components are designed for. Why did you replace the N47 head with the P90? Just curious, nothing wrong with a Frankenmotor if that's all you have available. So that's what that extra sensor in the thermostat housing is. Yes we did use the housing and sensors from the 79 in it. I will have to check the sensor to make sure its working correctly, and that makes sense now. The body came from my business partners son. To make a long story short, he got it from his father, it has only 74,000 miles on it. The interior is extremely nice, due to how they had stored it. He had taken the head off, and was going to rebuild it. But ended up finding a 74 which he liked more. That is why we didn't put the 79 head on the 82 block. He decided to do a v8 conversion on the 74. So we bought the car, and about 4 engines and tons of pieces, including mega squirt, 6 turbos including a brand new Garrett t3/t4, custom down pipes etc. for 1K. My son needed a car running in a short time, so we threw in new bearings, pistons, timing chain etc over a few days and stuffed it in the body for him to drive to a new job where he got transferred. So back to this car, after getting it fired up, it was running a bit rough and we found out in a short time the gas was bad. We drained the tank through the fuel pump and put new gas in. It was still a bit dirty and we pumped it out again. Put in new gas and it was running pretty good. I took it for a drive and it was running well, hitting on all 6 strong. Drove it around a few blocks expecting to seat the rings etc. So drove a bit further. Put in 20$ in gas and went and got it inspected, it passed. On way home, went around a corner and it started sputtering. Thought that was weird but started again, and got it home. That night when son got home started it up, ran a bit rough when cold (later found cold start injector was not working) but still started, and when warmed up ran pretty good. Then I took it for a bit longer drive, and it seemed to be using a lot of gas. Ran great and was going to take it on the highway. Before I got there, it started running rough and decided to head to the house. Didn't make it there. Even when cooled off. Next day, we discovered we were not pumping any gas, and found gas tank had a cracked seam. (So gas was going out it) So we took the tank from the 82 donor car that had been running great before son spun a bearing in, and the fuel pump, and put it in the 79. Then I thought the injectors might be fouled from all the trash, and pulled the whole fuel rail and injectors from the 79 and put them in the intake. Now he had to make his trip and I had to clean up my garage. I have been thinking about all this and doing other chores around the house. As my son says, compression is good, it has ran great at least for a hour, so I am thinking sensors or still trash somewhere in the lines. I will get a pressure gauge and put on the fuel rail. Then test all sensor back to the ECU, if that all looks good, and if I don't find anything, then it must be something with distributor even though spark looks good and timing is right. Remembering this has ran pretty good other than running rich. Enough rambling need more coffee and thoughts. Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 18, 2011 Share Posted December 18, 2011 It sounds like you had the right wires on the right sensors in the beginning,if you did all that driving around. Your other symptoms sound more like fuel supply problems. Maybe you got your connectors wrong at the thermostat housing. The extra sensor you're seeing in the thermostat housing is probably the thermotime switch. It controls power to the cold start valve so the engine doesn't flood when starting. It has the same connection type as the temp sensor and it's common to get the two switched since they're right next to each other. You can be sure which is which by testing resistance against the table in the FSM, then test at the pins at the ECU connector if you really want to be sure the ECU sees what it needs to see (corroded connections, shorted wires, etc., on the way to the ECU). The pin numbers are in the FSM Engine Fuel section, along with the resistance table. One turbo per cylinder will be new, looking forward to seeing that... Quote Link to comment Share on other sites More sharing options...
MadMaxDallas Posted December 23, 2011 Share Posted December 23, 2011 Thanks everybody for the starting pointers. I ended up wiring the temp sensor over to the cyl head temp sensor, and ran much better, cleaning a few connections and doing a regular tuneup will finish it out to running like it should. I do want to get a better fine tune on the fuel. I have not done it yet but was thinking since the 82 engine had a o2 sensor, of using that with a ohm meter to see if I can get it fined tuned at the afm. I will do a search on that. If not will have to take it to a shop with a c/o tester to get that done. Found a few other threads out there that helped a bit too. Especially on things like the resistance value charts etc in case somebody has these sort of problems in the future. Here are a few links to similar problems. http://www.classiczcars.com/forums/showthread.php?43173-Running-rough-then-stalls and this one http://www.classiczcars.com/forums/showthread.php?42574-MPG-timing-fuel-and/page4&highlight=mileage Thanks again guys. Even after building 4 engines now, these little beasts can trick you. Quote Link to comment Share on other sites More sharing options...
MadMaxDallas Posted December 23, 2011 Share Posted December 23, 2011 Looked around a bit, but i can not find a table for the 02 sensor (stock) I see that the wide band sensors should be around .5v would that be the same with the single wire sensor? I still have one miss to chase out but no more smoke etc. Seeing around .8 volts during idle and of course going up and down when I rev the engine. Quote Link to comment Share on other sites More sharing options...
MadMaxDallas Posted December 24, 2011 Share Posted December 24, 2011 (edited) Today found bad injector connector. Truly running like a sewing machine. Will take a little road trip from Dallas to lost wages on Wednesday and looking forward to giving it to my son to fix this beauty up! Edited December 24, 2011 by MadMaxDallas Quote Link to comment Share on other sites More sharing options...
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