Hey guys, checking in to see if maybe you could offer up some suggestions or if anybody has run into this problem and can offer some more insight.
Just swapped an 89+ motor into our buddy's car this weekend, and we're having some trouble with the wiring it seems. The car has fuel, spark and air. It will crank and crank but will not turn over. Sometimes, very rarely, we can get it to catch and it will run for about 2 seconds with no throttle response and will die immediately and that's all she wrote til it randomly starts again. Battery is good, fuel is good (car was running before this weekend). I have plenty of specific information, so we'll get right down to that.
-The motor was rebuilt (not very recently, mind you. Came from a car + parts buyout) and has ~1500mi on the rebuild [standard rebuild: head check and deck, gaskets, TB, WP, thermostat, etc]. Already oiled and spun by hand, timing re-checked, no bent or hit valves so all good there. We haven't checked compression or leakdown yet however. Motor was almost complete with wiring harness and starter, looks amazing inside the valve cover.
-Car has the later '87e body-side harness, with the round C101 and 3-pin C104 in the glove box. C101 is supposed to be plug-n-play, but we're going to check the DME pin-out vs. the body side C101 this evening. C104 #2 green wire (DME Start Signal / OBC Fuel Cutoff) has been run to each recommended location: the +15 post on the coil, pin# 27 on the DME, and pin# 7 on the C101 all without making any difference. We have confirmed 12 volts at the C104 wire during crank, which is switched by the main relay pin# 30 and verified. There is continuity throughout the harness between all above points when C104 is hooked up to the #7 pin on the C101, like there should be.
-The engine and harness are from an '89+ I car, and it came with almost everything already on it and plugged in properly so it was essentially supposed to be a drop-and-go. Starter, alternator, injectors, thermo sensors, CPS, oil level and pressure sensors were all checked and plugged in properly. Distributor cap and rotor were scavenged from the E motor, plug wire #6 was replaced with the correct wire that has the sensor attached.
-All relays are working properly; main clicks, ICV hums with "key-on" and has been checked, fuel and spark occur during crank. CPS verified good, tried my CPS and it didn't make any difference. Charcoal canister is not in the car but I don't run one in my car, although I do have the valve plugged in under the intake ('92 325i Vert). We unplugged it in my car and it started fine so we crossed that out.
-CPS and spark sensor have been verified and are plugged in the right location (replace the flywheel reference sensors from the E-car). Tried the CPS from my car and it made no difference. Spark has been confirmed with a test light, it is non-erratic and seems to be firing in time with the stroke. A plug ground against the cover shows strong spark. Fuel injector pulse has been confirmed with a NOID light, our noses and the plugs are wet. We let them dry out so the motor doesn't flood.
-Coil has .9 - 1 ohm continuity across the posts and shows voltage on crank. It's a really low voltage though... Multimeter read about 1V during cranking, but we do have a strong spark and the coil did work in the car prior to the swap. I don't know why it's so low, maybe the multimeter can't read it fast enough? We have plenty more coils to try if someone thinks that could be the issue.
-We haven't smoke tested it yet, but the only vacuum leak should be coming from the open port on the charcoal canister hookup under the throttle body, which we plug when trying to crank. The vacuum line for the brake booster has been modified. Late model throttle body has the 2 port hookup. One port has been blocked off and we re-purposed the line from the early model throttle, so there is vacuum between the booster and throttle body.
-Fuel lines are correct and have been verified. Feed is to the rail, return coming from the FPR. We haven't checked fuel pressure yet, but the FPR is correct and the car was running before the swap. Vacuum line is hooked up between the FPR and intake port. Crossover between intake and valve cover is new.
-AFM has not been verified, it was one of my spares. Plugged or unplugged makes no difference when trying to crank. A bad AFM shouldn't prohibit the motor from starting though. O2 is hooked up. He changed over to eBay headers and downpipe, so exhaust isn't complete yet but that won't keep the car from starting either.
-Bitch tube and dipstick were already in, nice and tight.
-Fusible link is good. Power distribution block in the front is hooked up correctly and wiring verified vs. a '90 325is, can't really hook them up backwards anyways. Fuse box ground on pass. side fender is hooked up and tight, engine ground on oil pan and body is tight, all starter connections are correct and tight, alternator connections are tight. All electrical connections on engine are hooked up correctly and tight.
-We used the fault code scanner on the diagnostic port. The only code that came up was for the AFM since we tried to crank with it both plugged and unplugged.
-All fuses have been checked and are good.
-His new DME is a chipped 153 silver label, but we have tried both a stock 153 silver label and 173 red label and it made no difference.
We've done plenty of M20 R&R's, M5x, S5x, etc. swaps into both early and late models, but for some reason this is wracking our brains! Any suggestions, even if they're listed above and can get a conversation going will help tremendously!
Thanks guys!
-Rob
Just swapped an 89+ motor into our buddy's car this weekend, and we're having some trouble with the wiring it seems. The car has fuel, spark and air. It will crank and crank but will not turn over. Sometimes, very rarely, we can get it to catch and it will run for about 2 seconds with no throttle response and will die immediately and that's all she wrote til it randomly starts again. Battery is good, fuel is good (car was running before this weekend). I have plenty of specific information, so we'll get right down to that.
-The motor was rebuilt (not very recently, mind you. Came from a car + parts buyout) and has ~1500mi on the rebuild [standard rebuild: head check and deck, gaskets, TB, WP, thermostat, etc]. Already oiled and spun by hand, timing re-checked, no bent or hit valves so all good there. We haven't checked compression or leakdown yet however. Motor was almost complete with wiring harness and starter, looks amazing inside the valve cover.
-Car has the later '87e body-side harness, with the round C101 and 3-pin C104 in the glove box. C101 is supposed to be plug-n-play, but we're going to check the DME pin-out vs. the body side C101 this evening. C104 #2 green wire (DME Start Signal / OBC Fuel Cutoff) has been run to each recommended location: the +15 post on the coil, pin# 27 on the DME, and pin# 7 on the C101 all without making any difference. We have confirmed 12 volts at the C104 wire during crank, which is switched by the main relay pin# 30 and verified. There is continuity throughout the harness between all above points when C104 is hooked up to the #7 pin on the C101, like there should be.
-The engine and harness are from an '89+ I car, and it came with almost everything already on it and plugged in properly so it was essentially supposed to be a drop-and-go. Starter, alternator, injectors, thermo sensors, CPS, oil level and pressure sensors were all checked and plugged in properly. Distributor cap and rotor were scavenged from the E motor, plug wire #6 was replaced with the correct wire that has the sensor attached.
-All relays are working properly; main clicks, ICV hums with "key-on" and has been checked, fuel and spark occur during crank. CPS verified good, tried my CPS and it didn't make any difference. Charcoal canister is not in the car but I don't run one in my car, although I do have the valve plugged in under the intake ('92 325i Vert). We unplugged it in my car and it started fine so we crossed that out.
-CPS and spark sensor have been verified and are plugged in the right location (replace the flywheel reference sensors from the E-car). Tried the CPS from my car and it made no difference. Spark has been confirmed with a test light, it is non-erratic and seems to be firing in time with the stroke. A plug ground against the cover shows strong spark. Fuel injector pulse has been confirmed with a NOID light, our noses and the plugs are wet. We let them dry out so the motor doesn't flood.
-Coil has .9 - 1 ohm continuity across the posts and shows voltage on crank. It's a really low voltage though... Multimeter read about 1V during cranking, but we do have a strong spark and the coil did work in the car prior to the swap. I don't know why it's so low, maybe the multimeter can't read it fast enough? We have plenty more coils to try if someone thinks that could be the issue.
-We haven't smoke tested it yet, but the only vacuum leak should be coming from the open port on the charcoal canister hookup under the throttle body, which we plug when trying to crank. The vacuum line for the brake booster has been modified. Late model throttle body has the 2 port hookup. One port has been blocked off and we re-purposed the line from the early model throttle, so there is vacuum between the booster and throttle body.
-Fuel lines are correct and have been verified. Feed is to the rail, return coming from the FPR. We haven't checked fuel pressure yet, but the FPR is correct and the car was running before the swap. Vacuum line is hooked up between the FPR and intake port. Crossover between intake and valve cover is new.
-AFM has not been verified, it was one of my spares. Plugged or unplugged makes no difference when trying to crank. A bad AFM shouldn't prohibit the motor from starting though. O2 is hooked up. He changed over to eBay headers and downpipe, so exhaust isn't complete yet but that won't keep the car from starting either.
-Bitch tube and dipstick were already in, nice and tight.
-Fusible link is good. Power distribution block in the front is hooked up correctly and wiring verified vs. a '90 325is, can't really hook them up backwards anyways. Fuse box ground on pass. side fender is hooked up and tight, engine ground on oil pan and body is tight, all starter connections are correct and tight, alternator connections are tight. All electrical connections on engine are hooked up correctly and tight.
-We used the fault code scanner on the diagnostic port. The only code that came up was for the AFM since we tried to crank with it both plugged and unplugged.
-All fuses have been checked and are good.
-His new DME is a chipped 153 silver label, but we have tried both a stock 153 silver label and 173 red label and it made no difference.
We've done plenty of M20 R&R's, M5x, S5x, etc. swaps into both early and late models, but for some reason this is wracking our brains! Any suggestions, even if they're listed above and can get a conversation going will help tremendously!
Thanks guys!
-Rob
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