88TPI406GTA

This fuse keeps blowing when I crank the car and I cannot seem to find a good circuit diagram for what uses this fuse and where it goes.

Car is a 91 Camaro, originally a TBI 305 and now a TPI 350 (7730 ECM)

I have searched through the archives and cannot find a definitive answer...any help would be appreciated.

Thanks!

88TPI406GTA

I should add that I suspect the problem lies on the path from this fuse to the ECM somewhere...I just want to make sure that I know what this fuse all powers.

TIA

88TPI406GTA

If I unplug all 3 ECM connectors and crank the engine, the fuse won't blow.

This is pin R of the C207 connnector, right? Should I see 12 volts at this pin when the key is on and the ECM is plugged in?

Vader

The CRANK fuse on most TPIs is for the cold start control (injector). IIRC, 1988 was the last year for that, so you still have one. Unplug the cold start control at the front of the intake coolant crossover or unplug the cold start injector and see if it still blows.

88TPI406GTA

Thank you for the response...I think that the reason there is a crank fuse here is that was originally an LO3 (TBI) and there needed to be a crank signal to the ECM for the injectors to fire...no need for that with the SD ECM (730).

I solved one problem though...I can crank the car (starter only) and the CRANK Fuse won't blow now. The problem was that the wire I had connected to D16 (ECM Ground) was the one that went to the crank fuse. So I disconnected that wire and now have a proper ECM ground.

It still won't fire and the injectors are the problem...I have plenty of spark.

However, did I blow my ECM by having +12 volts hooked to the ECM ground? The sensor grounds were hooked up and I am wondering if I shorted something as the ECM had other grounds available to use.

Vader

My apologies. In my haste, I missed reading the description of the vehicle fully and didn't understand it was a TBI conversion. The CRK fuse on the TBI was originally routed to the VSS buffer module. Since the 1227730 ECM has that function integrated, the buffer is not necessary. Unless the buffer module was left installed, the fuse should have no load.

If, through anaylsis of the wiring, you have determined thath the ECM had 12V+ applied to a ground terminal, it may have caused some damage. Do you know exactly which ECM ground pin(s) may have had 12V+ applied?

88TPI406GTA

Sorry for the delay...I am out of town currently in Bismarck, ND for funerals for two ND National Guardsmen killed in Afghanistan

Vader, the pin was D1, one of the system grounds...I noticed the A12 (I believe) is also a system ground...

What I don't understand is that the car ran until I wired up the P/N safety pin to ground and also ran the O2 sensor ground to the same ground.

How could the ECM not seek out one of the other grounds that was connected and have blown the fuse right away?

fcondebr

Hi,

I have just converted my 1991 RS TBI to TPI, and i'm getting the same behavior as you were.
The only difference is that my car is starting up normally, even finding out that the crank relay was missing near to the fuse box.
As i could read here, the crank fuse was being used by the vss buffer, which i have already removed. I don't think leaving it like this will matter right? Without the the crank fuse?! (eventhought, it is quit odd )
I think somebody did something to my car in the past to bypass the relay (cant find what it was done).
Well, my problem now are two:
1. Dome light, door and side mirror fuse keeps blowing. It is random. Sometimes it takes weeks.
2. Air bag light does not go away. I don't know why, but the aldl from the TBi is some how different. There iwas a light orange cable, i assume that it is from the airbag, connected to "M", and the serial ALDL was connected to "E". I've inverted these, and the computer started to read the ECM. After that, i've decided to jumper both cables, but now ECM works and Airbag light stays on. If i turn off the ECM, the air bag light goes away.

Any ideas?
Thanks inadvance