Hi Guys,

I thought I would try this again since my other thread was going nowhere!

I HAVE to fix this soon, because it's in my parents driveway and they're going apeshit. It's been there for months, I've got over 40 hours into chasing this problem and I can't seem to get it sorted.

Originally I thought it was a VATS issue, as followed by this thread. But I found a old gm vats .pdf that clearly stated that if the Security light turns on, then off the vats is functioning correctly, and is in "normal operation"

If It was blinking I would think I could just reset it, biased on this. But its not.

Summary
-Cranks but doest start
-No Injector pulse
-Fuel pump does not prime, but turns on if ALDL is jumped from port G
checked at rail, shows pressure when jumped
-New distributor, to eliminate ICM as possible issue
-No code 12 w/ OBDI scanner


Then I deiced to check for voltage over the under-hood ecm fuse with ignition switch in the "on" position, and got no voltage. Weird. I'm assuming this is the right thing:



I thought this might be my issue, so I cut it to fix some shady wiring, because one of the wires was frayed. Now an open circuit, I expected to find NO power at the ECM.

but then still got power from all the colored pinnouts:





So I would assume that there are more "live" wires going to the ECM than just the two main ones Rbob mentions here.

... and the ECM simply opens ground to the circuits which already have a power in (i.e. the colored points)

So my questions are:

Should I have power at these pin-outs?
Am I missing power at any pin-outs?
Despite the fact the security light comes on, then off, is it likely vats is disabling the injectors and FP?
How do I check for DRP?
What are your recommendations for my next plan of attack?

I NEED to make this thing work ASAP!

Thanks Guys!

 

Bump

I really need help guys, I have done a ton of digging on this site and not found much, anyone?

In my last tread somone mentioned checking to ensure the FP is activating correctly, but I can't shake the feeling this is a secondary issue, stemming from an ECM issue. Either the ECM not reciving correct power, not reciving drp or readings from the oil pressure switch or a issue with Vats disabling the fuel system.

Thanks!

 

Bump

I really need help guys, I have done a ton of digging on this site and not found much, anyone?

In my last tread somone mentioned checking to ensure the FP is activating correctly, but I can't shake the feeling this is a secondary issue, stemming from an ECM issue. Either the ECM not reciving correct power, not reciving drp or readings from the oil pressure switch or a issue with Vats disabling the fuel system.

Thanks!

Is there a way to check the wiring to the FP without tearing out the axel?

 

Not getting a code 12, and pump not priming would lead me to think either ECM or wiring issue. Check the fusible links at the starter also maybe loose or broke wire there? Could be why you have no power at the ECM fuse

I didn't look at your previous threads, but what happened? Did you do any repairs to the vehicle before this? Or did you come out to drive one day and it no longer started? Do you have 12v at the injectors?

 

pretty popular link today. Here is some info on VATS, just to eliminate that as a problem

https://www.google.com/url?sa=t&rct=...08538919,d.dmo

 

Out of an '88 service manual for your engine. Looks like it may be the ECM.

 

I was thinking that also, but since he's not getting power at the ECM fuse I'm leaning more towards the power junktion at the starter with the fusible links.

Also VATs disables injectors and starter. Fuel pump would still prime. Since the security light goes out and the engine cranks I would not go down the path of troubleshooting a VATs issue.

Find out why you're not getting power supplied to the ECM/FP fuse and you'll find your problem

 

Make yourself a check-light (aka a light bulb with two wire coming off it) and veryify that you are:


A) getting fire TO the distributor
B) getting fire FROM the ICM


I know you replaced the distributor, but I also know (from personal experience) many "new" ICM's are junk.

 

Wilco, I'll post results. Should be week after next since I have exams next week.

Does it? From the reading I've done it only disables ECM controlled Fuel system functions. Remember this started as a VATS issue, and performing the VATS bypass with an inline resistor seemed to help (the car ran for a while).

Not to say your incorrect, but I have no Idea what you are talking about, I have done a starter on a third-gen three times and never seen any fusible links. Do you have a picture of what they should look like, even better, their location? As far as I can tell its only a bunch of ring connectors which mount to the starter's power connection.

I don't think it would be, before I noticed lack of a code 12, at which point I was getting the security light to come on, then turn off as it should, I swapped ECM's to test for that problem. I also tried this after I noticed this issue. Regardless, I think it has more to do with a lack of power to the Under-hood ECM fuse, which bizarrely does not mean no power at the ECM pin-out connector. As I mentioned earlier in this thread, I still have no idea which pin is the one I should be checking for Voltage at the ECM while trying to fix the underhood ECM issue, nor do I know how many volts/amps I should feed through the under-hood fuse-to-ecm wire to test it under load without frying it.

The car has been sitting for a few months, but seems to crank ok. Perhaps low battery voltage is a factor? Who knows.

I'm going to purchase a FSM, I found one here. Is there a better place to purchase one?

 

 

 

That's an underside shot. The main wire from the battery goes to the large terminal on the starter, there are 3 thick wires with fusible links on that same terminal.

The Vats module grounds the starter relay. Incorrect resistance value-module doesn't ground relay-starter doesn't crank. Of course it is possible over time that the start enable relay was wired to ground.