I am planning on changing out all of the gauges in an 88 car. My choices are mechanical vs electrical gauges for water temp and oil pressure. Does the engine management system need any signal from either of these to operate properly?

If not, it seems that it might be better to use electrical for the water temp (with a new sender)and either for the oil pressure. I have had problems with the stock electrical oil pressure gauge failing during a session where the mechanical would be less likely. Of course, there would be oil in the dash with a mechanical gauge.

Second question for smarter people. If I redo the wiring, the fuel pump would be on a switch.

With a switch, the pump will be running all the time that the switch is on. Is that any problem? I assume that it runs all the time with the current system when the engine is running. Is that correct? Is there any concern with wiring the fuel pump to a switch?

Third question. Is there anything in the fuse box that would need to be retained with a rewire of the car? I plan on keeping the engine harness but nothing else.

Thanks for the help.

Big Dog

The DME does not need the signal from these sensors. There is a separate water temp sensor for the DME and the oil pressure sensor is for the guage only. If you want to use the stock wires instead of running new ones they run to the 9 pin connector above the brake booster.
I use electric guages as I don't like the idea of oil or coolant in the car above my legs.
An aftermarket tach can also be run off the DME signal wire. Pin 21 in a 87 924s. Which runs to the 4 pin connector about 6" from the DME.
You can run the fuel pump off of a switch but I still recommend it being fused. I still use the DME relay and a circuit breaker which I ran to a switch.
I have eliminated the entire stock fuse box and run circuit breakers instead. Very time consuming but I think it was worth it.

Thanks for the info. I am planning on rewiring everything except the engine harness to get rid of 20 year old wire. I plan to remove the fuse box and replace that with fuses on a panel inside the car so everything will be fused.

Do you know if the fuel pump runs all the time the engine is running or does it run on demand for fuel? I assume it runs all the time but would like to be sure.

If I redo all the wiring and junk the fuse/DME relay box, how would I retain the DME to control the fuel pump so it shuts off when the engine stops?

Is there anything in the fuse box that needs to be retained to make the car run? My thought is to remove it and all of its relays and other stuff completely.

Big Dog

To hold the DME Relay I used a relay harness plug that I picked up at Carquest. I did the same for the cooling fans and wipers. I'll try to find the info on them for you. I've removed the entire stock fuse panel and just kept the 3 relays and a few fused links.

If you are looking to remove everything you may want to look into a universal chassis wiring harness. They can save you alot of time and energy but I'm not sure how much you want to spend to do this. Painless performance is one of the many suppliers for them.

Jim,
Pump runs all the time with the "key on". The pump just puts fuel to the rail. Excees fuel gets send back to the tank.

Thanks, all, for the information. I will await info on the relay harness plug information if you have it.

Jim