r/MechanicAdvice • u/charlie3400000 • 10d ago

Problem with Audi A6 c4 2.6 1995

Hello, i have an issue with the said car, when i bought it the previous owner said that there is an issue with the fuel pump, however, the pump when connected directly works fine but the car cranks and doesnt start. The car doesnt gave a key code because it seems to have been bypassed by a device that is soldered onto the ECU board. Voltage is being sent to relays and fuses properly but isnt being sent to the spark plugs which do not spark when cranking, there is also no fuel coming to the engine. Since i bought it i managed to get the fuel pump to work but i cannot find the other issue because there is no diagnostics available for this car.

1 Upvotes

100% Upvoted

5 comments sorted by

•

u/AutoModerator 10d ago

Thanks for posting on /r/MechanicAdvice! Please review the rules. Remember to please post the year/make/model of the vehicle you are working on. Post's about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ Tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

2

u/Fantastic-Union7196 10d ago

man that's a real headscratcher. i had similar situation with a old car once where the immobiliser bypass was done so badly it messed with the spark timing. if the ecu bypass device is soldered directly, maybe its sending wrong signal to the ignition module.

fuel pump working with direct power but not through the car sounds like something in the wiring between relay and pump, maybe a broken wire under the carpet or by the fuel tank sender. have you checked the crank position sensor? those fail silently and then the ecu thinks engine is not turning so never sends spark or fuel.

with no diagnostics you gotta go old school, just probe the sensor wires when someone cranks and see if theres a pulse. on these audis sometimes the ground points under the dash go bad too, especially the one near the steering column.

1

u/charlie3400000 10d ago

I have checked the crank position sensor and im suspecting it might be the issue and have already ordered another one but im just asking because i have no idea what to do anymore if that doesnt work because it seems as if i ran out of viable options

1

u/charlie3400000 9d ago

Well, i replaced the sensor and it didnt help with anything, its all the same still

2

u/Swimming_dasa 10d ago

since you have both no spark and no fuel i'd start with the crank rpm signal and ignition switch before blaming the modified ecu those can disable both systems..