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Stalling Issues

Timmy2tone

Timmy2tone

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I have a '90 Blazer that runs great until she doesn't. The issue I'm having is a fuel delivery problem when the truck is driven for 20-30 mins. I lose power to the fuel pump. It does start after I sit and let it cool off. I've replaced the fuel pump, fuel pump relay and fuel filter. I did check grounds and found the main ground coming off the battery going to the manifold had a little corrosion. I put a new cable on and thought I had it figured out until it shut off on me 10 mins. from the house. I raised the hood and the fuel pump relay was pretty warm to the touch, not sure if that's normal. If anybody has run into this issue please tell me how you corrected it.
 
Are you sure the fuel pump has lost power at this point ? The ecm won't trigger the injectors if the ignition control module has failed. The 20 mins and dies wait a bit and runs is a common ICM symptom
 
I replaced the ICM January and probably have less than 100 miles since replaced. I was having the issue before I replaced it. Should the fuel pump relay get hot normally? After it stalls I turn the ignition off for a few minutes turn it back on and the fuel pump does not come on to prime. After it cools for 20 mins .or so you can turn the key and hear the fuel pump kick on and then she starts.
 
Wes Harden said:
Are you sure the fuel pump has lost power at this point ? The ecm won't trigger the injectors if the ignition control module has failed. The 20 mins and dies wait a bit and runs is a common ICM symptom
Click to expand...
I replaced the ICM less than 100 miles ago because i was having the stalling issue
 
Not really, warm maybe but not hot. It could very well be high resistance causing a low current to fuel pump. How do the the terminals look in the connectors ?
The 10ga red wire at fuel pump relay is a "test" wire add 12v and fuel pump should run. Double check the ground at the tank, it should be screwed to the cross member in front of the tank
 
Wes Harden said:
Not really, warm maybe but not hot. It could very well be high resistance causing a low current to fuel pump. How do the the terminals look in the connectors ?
The 10ga red wire at fuel pump relay is a "test" wire add 12v and fuel pump should run. Double check the ground at the tank, it should be screwed to the cross member in front of the tank
Click to expand...
I do have a fuel pump ground on the driver side frame rail. I cleaned that up as good as I could. I did turn the Key on with that ground not bolted to the frame rail and the pump came on.
 
Wes Harden said:
Not really, warm maybe but not hot. It could very well be high resistance causing a low current to fuel pump. How do the the terminals look in the connectors ?
The 10ga red wire at fuel pump relay is a "test" wire add 12v and fuel pump should run. Double check the ground at the tank, it should be screwed to the cross member in front of the tank
Click to expand...
I do have a fuel pump ground on the driver side frame rail. I cleaned that up as good as I could. I did turn the Key on with that ground not bolted to the frame rail and the pump came on.
 
if pump ran with tank ground off, I am guessing you have 4 wires and a second ground for the pump
 
Timmy2tone said:
I'm not sure .I had a buddy helping me install the new pump and I really didn't pay attention. I know i connected the ground to the frame rail.
Click to expand...

Wes Harden said:
if pump ran with tank ground off, I am guessing you have 4 wires and a second ground for the pump
Click to expand...
Probably. If the ICM is getting hot can that make the ecm shut down the fuel pump
 
idk about shutting down the fuel pump, but it won't signal the injectors to open. I need to look that up.
 
Just test the pump as Wes instructed. 12v to the red wire when the relay won't trigger the pump to prime with key on. It seems unlikely given your symptoms, but need to rule that out first.

FYI there is a delay (probably 15 seconds) between key on/off events before the ECM will run it's prime cycle again.

Inspecting the plug/connectors/wires is necessary as well.
 
dyeager535 said:
Just test the pump as Wes instructed. 12v to the red wire when the relay won't trigger the pump to prime with key on. It seems unlikely given your symptoms, but need to rule that out first.

FYI there is a delay (probably 15 seconds) between key on/off events before the ECM will run it's prime cycle again.

Inspecting the plug/connectors/wires is necessary as well.
Click to expand...
I figured there was a delay but even waiting 1-2 mins. turn the key on and no fuel pump. It has to sit at least 20-30 mins before it cools off enough to restart.
 
Timmy2tone said:
I figured there was a delay but even waiting 1-2 mins. turn the key on and no fuel pump. It has to sit at least 20-30 mins before it cools off enough to restart.
Click to expand...

That's why you try and force the pump to run with the 12v lead. If the pump won't run that way, the problem is between the tank and relay.

If the pump does run, it's between the relay and ECM.
 
You also need to check the power to the relay during ignition on. Check for the 2 second run and the continuous ignition power. If those are not getting power, it is the ECU or the wires to the pump. I had a switch on the Jimmy that ran the pump contiguous when the relay died on the trail one year. Shut it off manually. You could try that to make sure the pump wiring is not the issue.
 
ktmoutfront said:
If those are not getting power, it is the ECU or the wires to the pump.
Click to expand...

I assume you mean wires to the relay, not the pump?

My gut says Wes is onto something with the shutting off when hot, but IMO rule out the basics/easy stuff first. The pump can be tested alongside the road in two minutes.

Other causes could be the culprit, and are more likely given the symptoms, but the ignition/fuel circuit is far more complex than the fuel pump to relay portion which couldn't be easier to test.
 
I know you said the pump was new, but running well then stall wait 20 mins to run again always says to me bad pump. What brand and where was pump sourced.
Hot relay and wiring can also point to a pump failing.
 
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