ANDYZ28

I have owned an '86 IROC-Z for several years and it is currently awaiting the repair and restoration to be completed. But it has been very hard to start, unless I pour 1 ounce of fuel into the intake bellows. Then it start right up and runs.

Can/should I use the GM diagnostic procedure to determine the cause? I would prefer not delete to cold start injector if possible.

Thanks, Andy

85Iroc-Z

iTrader: (4)

Have you checked fuel pressure? Can you hear the fuel pump run when you turn the key on?

ANDYZ28

The pump runs and primes the system, pressure is 39 PSI as best I can determine. I have a Snap-On scan tool if it will help me?

Bob88GTA

iTrader: (2)

Oil Pressure switch operational?

ANDYZ28

No too sure yet. I have the original GM manual, I will diagnose it tomorrow. EGR valve stuck open sounds like it might be the culprit though.

DENN_SHAH

iTrader: (1)

if the EGR valve was stuck open, then the motor would run very badly or die at idle.

i don't think there is a reading for the cold start valve/switch in the scanner, so you need to test it using the procedure from the book.
but there is other useful info you can get from the scanner.
i've repalced many cold start switchs over the years.
also its not unusual for the cold start valve to stick closed if it has sat for a while.

ANDYZ28

The clod start switch appears to be a "normally closed" switch, providing a path to ground for the "cold start" valve. Above 95 degrees F the switch would be open, thereby preventing the cold start valve from functioning.

Thanks, Andy

DENN_SHAH

iTrader: (1)

i didn't remember the temp it opened up at.
also if you replace the switch, don't use teflon tape on the threads as it can cause the switch to not have a good ground.

i should have read my post as i left this out.
the hot side of the cold start injector gets powered thru the crank part of the ignition switch so it can only activated during cranking.
as a quick check of the electrical side, if you have one you can plug a noid light into the CSI connector & with the engine below opening temp of the cold start switch crank it & see if the light turns on. a test light or a dash light bulb will work in place of a noid light.

ANDYZ28

It was raining yesterday, so I copied the appropriate pages from my original GM service manual (1988) and went to work on diagnosing this problem. Getting access to the cold start switch (CSS) was no picnic either, as the alternator support/adjustment bracket had to be removed, stubborn rusty bolts, etc. ...................Anyway I discovered that the 806 circuit (purple wire) had excessive resistance (above 20 OHMS) and when I tested at the connector, circuit 832 (Tan wire) I did have battery voltage (BV) in the crank position. Result, CSS failed and when I get some $$$ I will replace it. I check some prices for a replacement CSS and they are all well above $100, which is not currently in the budget. I grounded the 832 circuit at the connector with my Kent-Moore diagnostic probe and the engine started right up.

As I mentioned earlier, this project car has been setting for literally years, and once it started it did not seem "happy". Three cylinders were not firing, I found a failed spark plug at #4, and finally got the injectors on cylinders 6 and 7 working by tapping on the injector body with the handle end on my long handled Snap-On 3/8 drive ratchet. I also had to replace the bad fuel by pumping/draining the bad fuel into a separate container from the injector return line. I put about 100 miles on it and now it runs great. I will replace the cap/rotor/wires at a later date. But for now I am pleased with it.

I hope this info will help someone in the future who may have this same issue. I can take a photo of the service manual page if someone can post it on this thread?

Thanks, Andy

I see that in a couple of months I will have been a member for 15 YEARS, WOW!

DENN_SHAH

iTrader: (1)

instead of replacing the temp switch, something you may want to look into is upgrading the chip in the computer. the newer systems didn't use a cold start injector. the only changes from what your car has is no cold start injector, and the chip. with a chip change you can leave the cold start injector in place, just unplug the harness from it.
there are a few members here that can help you with a replacement chip.

there are a couple of posts i made where the car had sat for a while & the injectors were stuck closed.
i would figure a complete injector replacement is in your future.

nice on the 15 year membership.

ANDYZ28

When I installed the "as new" engine and entire drive train, it did the same thing. A fellow technician said "wait until it comes up to temp", he the tapped on the injectors, and each one came to life. That was thousands of miles ago.

Thanks, Andy