Killing ICM's?

[SCOTTYINWV]

Sometimes the icms won't test bad until they are hot. I usually make them test it multiple times in a row to rule it out since each test heats it up more and more.

 

[great white]

Check for spark?

If no injection and no spark it's likely icm or potentially the dis pickup.

Fuel pressure test is a good way to go if you have spark, although icms have been known to fail to trigger the ECM for injection bit still trigger spark...

 

[thunderstruck]

20 years? I've had my '97 about 3.5 years & I've replace the fuel pump 2X! And I'm like you in the fact that I never let the tank get below 1/4!
Damn offshore crap!

What brand(s) of fuel pumps are you using?

My original one quit at 15 years, 204k miles.

 

[gmcyukondriver]

Ok, new ICM is in, still won't start. Too frustrated to go anywhere near it right now, I'll probably check for spark in an hour or so. If no spark, I'm guessing it's either the pick-up coil or the external coil. In either case, I'm narrowing things down, just a little more slowly than I'd hoped. At least I don't have to get to work for the next couple days.


BTW, I gave my mechanic a call and he said that the computer won't signal the injectors to start up until it detects spark, so that could be the reason why my injectors aren't firing.

I'm also getting really good at pulling my distributor cap.

 

[great white]

Wait, is this a hard start or a no start scenario?

Two different things...

 

[gmcyukondriver]

Well, it used to be hard start. I would have to crank it for about 10 seconds, then stop, then crank it again and it would fire. Sometimes, it would fire, but just barely (not enough to make a grinding noise on the starter if I kept cranking), and once I turned the key back to "ON", it would raise RPM and idle fine.

It has never died on me once it's started, it's just been hard to start.

Yesterday, I drove to the store, came out, and it would not start. Tried for about 10 seconds, gave it a 5 second break, then another 10 on, 5 off, and a 10 on again. Nothing. I didn't want to over-work the starter, so I gave it about 20 minutes, then tried the same procedure. No start. Got it towed home. Tried it again, nothing.

Tried it this morning, nothing. Pulled the ICM, had it tested, it passed. Came home checked the injectors, and they aren't spraying. Replaced the ICM, still nothing. Just got an in-line spark checker. It tests good, so it's a fuel issue.

I already have a pressure gauge on it, so I'll check that in the morning, but I'm going to start with fuel relay and fuel filter.......because if it isn't those then it's the fuel pump, and I just filled up 2 days ago.....so the tank is going to be a pain to drop.

 

[gmcyukondriver]

So it's not the fuel pump relay. Just installed a new one, same thing. I'm going out to check fuel pressure now.

Quick question, how often do you guys change fuel filters? I think the one I have in there now has about 30k miles on it.

Just to recap:

Injectors aren't cycling.
It cranks just fine.
I am getting spark.
Ignition Control Module is new.
Fuel Pump Relay is new.

It will not start, had a hard start issue for about a week, but once it started, it drove just fine. It never died on me, just wouldn't start.

 

[gmcyukondriver]

In-line gauge reads no fuel pressure when key is in the "ON" position (not start or running). Going to grab my multimeter and make sure the pump is getting power and is grounded correctly.

Anyone know where it's grounded or the best places to check to make sure it's getting the proper voltage? I'm also going to check where the fuel pump relay plugs in, just to make sure it's getting power there.

 

[98_k1500]

Pull the fuel cap off, get a helper to turn the key on, and see if you can hear the pump. May be the rubber hose inside the tank if the pump is running but no pressure. I had a jeep do this. If you are not getting power, Jump terminals 87 and 30 on the relay. (pump should run key on or off) If the pump runs then, the computer is not telling it to run (oil sending unit maybe, not sure on a tb motor) If you are getting power, but the pump is not running, pull out your reciever hitch, have a helper cycle the key on and off rapidly, and beat the living **** out of the tank. If the pump then primes, crank it up and run it as long as you can. Pump is bad and the more gas you burn, the less you have to deal with being in the tank when you drop it.

 

[great white]

Oh boy, pretty sure where this is going to end up......