thtanner

iTrader: (1)

Lots of pictures in this thread. Everyone likes pictures.

Long story short, the car has always had cold start issues. Engine rebuild, new fuel/ignition system later.. same thing.

Had 3 mystery wires floating around when I bought the car, had a thread up for a while and could never pin them down.

WARNING: Filthy engine! Was when I bought the car before giving it love.


Fast forward to today, I wanted to replace the oil pressure switch since that's the last thing in the chain of hard cold starts that I really have left. I crawl under the car to make sure of what it looks like before hitting the parts store so I don't buy the wrong thing. Engine was changed so you never know. This is what I am greeted with..



De nada. Nothing.

For reference, it should have something like this...

.

Now.. when the engine was rebuilt they hid the wires.. or worse, cut them down in the harness. I gotta find them, but that's somewhat the easy part really.

What do I do about the missing oil pressure switch? I hate the cold starts, and, I'd love to figure something out. I saw something like this on a c4 vette, maybe I can do something similiar?

thtanner

iTrader: (1)

I'll get back under the car tomorrow, but I may have missed the plug (due to a heavy coat of paint). If it's plugged off it'll be as "simple' as removing the plug, finding wires, fixing wiring, and plugging back in.

We'll see.

Example:

357L98

iTrader: (1)

I don't think adding an oil pressure switch will help your starting problem. The ECM runs the fuel pump when you turn the key on.

thtanner

iTrader: (1)

The ECM primes the fuel pump, but does not keep it running 100% during cranking. The oil pressure switch kicks it up during that time. My pressure drops a little between the prime and and the ECM firing up the pump(4-5 engine revolutions), with the OPS it will keep fuel pressure consistent as the pump will stay on (should trigger the switch with a half revolution of the engine)

I've replaced every single component relating to fuel or spark, literally every one. Last piece of the puzzle here Every other TPI car I see cranks fairly instantly cold, and this particular piece differs on my setup, so it seems the likely culprit.

Step 1: put it back to stock
Step 2: see what happens

357L98

iTrader: (1)

Well, I hope it helps. The reason I don't think it will make any difference is that I have transplanted TPIs onto older carbureted engines, and deleted the oil pressure switch just to save some complication. They start instantly. The engine will fire on the fuel pressure already in the lines, and then the pump is on again.

If you want to test this the easy way, connect a jumper to your fuel pump relay so the pump is running and stays running the whole time you are cranking. Then you'll know.

johng1

iTrader: (1)

We did something very similar to your picture when we did my motor swap. We went to home depot and bought a brass "T" and plumed in both oil pressure switch and the one that goes to the gauge in the dash. It worked perfect.