C41 advice needed
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
C41 advice needed
some advice please I bought a non running
91 L98 auto car with a serial data loss of comms issue
i have read every post on here i can find and have followed the tests
checked fuses,cleaned and checked grounds, swapped in and out a working ccm. Fitted a working prom to the ecu with appears to be new delco raman.
checked fuel pressures checked injectors resistance and with noid lite and there pulsing, new tps fitted new ignition module fitted new plugs fitted , bypassed serial data and connected ccm to ecu and it communicates c12 and no error on 4 but still wont start but for a second or 2 like a timing issue and i suspect the ecu has been killed but need to sort c41 before throwing more $at it.
what i have is power to one of the 2 tan serial data wires at the red plug at ecu 12v interiour lite off 1+volt lites on and can be o volts with courtesy lite fuse pulled pulling the relay has no effect
any ideas where to check. Iv been on this on and off for a month and need some fresh ideas. As im having trouble tracing the source of the problem
91 L98 auto car with a serial data loss of comms issue
i have read every post on here i can find and have followed the tests
checked fuses,cleaned and checked grounds, swapped in and out a working ccm. Fitted a working prom to the ecu with appears to be new delco raman.
checked fuel pressures checked injectors resistance and with noid lite and there pulsing, new tps fitted new ignition module fitted new plugs fitted , bypassed serial data and connected ccm to ecu and it communicates c12 and no error on 4 but still wont start but for a second or 2 like a timing issue and i suspect the ecu has been killed but need to sort c41 before throwing more $at it.
what i have is power to one of the 2 tan serial data wires at the red plug at ecu 12v interiour lite off 1+volt lites on and can be o volts with courtesy lite fuse pulled pulling the relay has no effect
any ideas where to check. Iv been on this on and off for a month and need some fresh ideas. As im having trouble tracing the source of the problem
Thanks in advance
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Do you have factory service manual? If not, you need to get a set. Stock radio? Injector pulse and fuel pressure? Compression? Verify distributor rotor is pointing to # 1 or #6 when timing mark on balancer is at 0 on timing tab. Ideally if you check compression on either 1 or 6 the you can verify timing when either cylinder is at TDC on compression.
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
Do you have factory service manual? If not, you need to get a set. Stock radio? Injector pulse and fuel pressure? Compression? Verify distributor rotor is pointing to # 1 or #6 when timing mark on balancer is at 0 on timing tab. Ideally if you check compression on either 1 or 6 the you can verify timing when either cylinder is at TDC on compression.
No i dont have the fsm but i am looking at a setTdc on number 1 and leads in correct firing order Good compresion Aftermarket radio and i do have sys on dash clusterIm going to install new dizzy cap ,leads and rotor and see if it makes a difference
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
Iv done the above. And will kinda run on 4or 5 cylinders only.
Drifting
Joined: Feb 2008
Posts: 1,538
Likes: 178
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
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Supporting Vendor
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Easy to do if either engine or trans has been out of vehicle !!!
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
So its 2 issues ; bad ecu and it is a ck 800 power to circuit issue.wich most likely fried the ecu, Im just having trouble tracing it. It seemes to be from the rear of the vett in a black wire that connects under passenger foot well
Oil Producer
Joined: Apr 2014
Posts: 9,388
Likes: 2,749
On my 86, which i know is way before 91, there was a wire bundle that dropped out near the passenger door hinge on the inside of of the car, then ran towards the rear at at the base of the door sill, up over the rear passenger rear wheel well, then it turned towards the rear hatch latch, and to the antennae. it powered many things slong ghe wat and i do belive thre were a few ground locations aling the way. iff the top of my head i believe it powered the halo lights, rear window defroster, rr speakers, rr lights, antenna, rear latch solenoid, fuel pump.
is this the kind of thng where you peel out the interior and follow that wite bundle all the way back inspecting every inch of it? probably a ground rotted out or trin screw too long and it pierced the shielding and is causing intermittent ground?
Sorry im not of more help, dont give up, sounds like sll you need is the ck 800 routing diagram now.
Last edited by VikingTrad3r; Feb 17, 2018 at 10:17 AM.
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
this is a good thread because its these types of problems that far beyond the average dnthusiasts ability to diagnose and fix, including mine!
On my 86, which i know is way before 91, there was a wire bundle that dropped out near the passenger door hinge on the inside of of the car, then ran towards the rear at at the base of the door sill, up over the rear passenger rear wheel well, then it turned towards the rear hatch latch, and to the antennae. it powered many things slong ghe wat and i do belive thre were a few ground locations aling the way. iff the top of my head i believe it powered the halo lights, rear window defroster, rr speakers, rr lights, antenna, rear latch solenoid, fuel pump.
is this the kind of thng where you peel out the interior and follow that wite bundle all the way back inspecting every inch of it? probably a ground rotted out or trin screw too long and it pierced the shielding and is causing intermittent ground?
Sorry im not of more help, dont give up, sounds like sll you need is the ck 800 routing diagram now.
Thread Starter
Heel & Toe
Joined: Jan 2018
Posts: 19
Likes: 0
From: Ca
Running the tests from the factory service books i have no continuity from e13 to b11
i dohave continuity on b5 but also have 12v at b5 and no ground e13 to ground test
any c4 wiring guys that can point me straight. Im considering rewiring crk 800 data wires ,i know its a shorcut but i think may be my best option
i dohave continuity on b5 but also have 12v at b5 and no ground e13 to ground test
any c4 wiring guys that can point me straight. Im considering rewiring crk 800 data wires ,i know its a shorcut but i think may be my best option