Hi,

What is the function of the charge air overpressure switch? Does it cut off fuel when the turbo goes beyond a certain boost (what pressure?) Does it also retard the spark? And is there a good troubleshooting procedure to determine if it is operating correctly?

Thanks,
Charlie

Hi Jimmy, Thanks for advice on the knock sensor. It's good to know that disconnecting the knock sensor causes the timing to go into "limp mode". Conversely, is there a way to fool the engine management system into thinking the knock sensor is good and there is no need to retard the spark? ...

Hi Bill,

Well, the 5th gear OD fixed itself before I could do any troubleshooting. Darn! But you've given me the tools to dive into it if the problem returns.

Thanks,
Charlie

Hi Bill, Thanks for recommendation - I never thought of that. I put marks on the outer edge of the damper and the inner hub. The strobe light shows them tracking together. So it looks like the damper is solid. Now I'm back to tracking down what components are involved in the spark timing. Do you kno...

Hi, I'm experiencing some strange problems with a 1988 740 Turbo wagon I'm working on with my nephews. Over the summer we installed the motor from a 1993 940 Turbo. We kept the harness and electronics from the 1988 car. The car ran fine for several months. Now we have a strange problem - under load ...

Thanks! I'll try it over the weekend.

Hi Bill,

Thanks for the reply. Fuses are OK and the dash light is not coming on. I even short circuited the shift button in 4th and nothing happens. So it sounds like it might be the relay. Where is it located? Do you have an online troubleshooting manual you can point me to?

Thanks,
Charlie

Hi, My 1988 740 Turbo manual transmission is not shifting into overdrive. I checked the fuse and it's OK. Is there a simple way to determine if the problem is the 5th gear microswitch on the gear knob or the solenoid on the transmission? If I short the switch, should that kick in the overdrive unit?...

Hi, My 1988 740 Turbo Wagon is not putting out any power at low rpm under load (2000-3000 rpm climbing up a hill). The engine has absolutely no power. There is boost showing on the gauge. It feels like spark is way off or mixture is lean under these conditions. There is no pinging or obvious misfire...

To All Interested in This Post, Check out the posting "Troubleshooting Guide or Tutorial for 1988 Jetronic?" Bill of Durham was kind enough to attach a guide that has many of the details of testing the LH Jetronic on the 1988 model year. Many of the tests can be done with an ohmmeter and v...