96 blazer stalls when hot

[MT-2500]

Originally Posted by maxisp2000

That sounds right. When it gets too hot outside, maybe the pintles or injector leak and the car floods hot.
But I would think that there is a code for too rich, beyond tolerances.
When my fuel pump went out the code set was for one bank too lean, it was symptom of low fuel pressure.

Fuel pressure problems do not always set code.
If pump quits all at once the computer can not tell anything
That is why they make fuel pressure gauges.
Get the pressure gauge on it and drive it and wtch it.
Post back all pressure readings.

[maxisp2000]

Timing advance.
It's -20 at start and goes to -40 on acceleration.

Short trim timing -2 to -5 on bank 1 and 2 and about the same for both banks long term.

There are no codes stored, none pending and none permanent.

Tomorrow is going to be hot I will see if I can duplicate failure.

[mcdon26]

I currently have a pressure gauge hooked up to the schrader valve on the fuel rail. Can you explain how where to place a pressure gauge to test the pump itself prior to being adjusted by the regulator?

I wanted to run through an entire tank of gas and get pressure reading throughout. If memory serves correct, my problems usually are when I am below a half tank of gas and when it is above 80 degrees outside. Interestly enough, Once I hit half a tank, pressure readings became a little more eradic. Specs while driving were about the same as previously reported, however, the needle was much more "jumpy" or "jiggly" or eradic. I should take a video and upload it. Now for the more interesting part. When parked and in nuetral, and below a half a tank, I would rev the engine I would get a smaller spike in pressure as before but as I revved up to 3000, the higher the rev, the lower the pressure would go (ended up below 55. Again, previously I would get a spike in pressure and an immeadiate return to 55-58 psi. This occurred when I was below half a tank. I also do have a leakdown issue that has seemed to increase now that I am below half a tank. I am going to check it at hour intervals today and record the pressure. I waited to fill up so I could get these readings and will subsequently record the same reading after fill up. To bad I waited to fill up though, gas around here went up another 6 cents per gallon since yesterday.

[mcdon26]

I've taken some videos to at least show what I'm talking about, the first video is to give some perspective on the pressure gauge dial as it's a little hard to video it close up while driving. Here is the link to the first video. you should be able to see the rest in my channel. Let me know if you cannot.

http://www.youtube.com/user/mcdon26?.../5/RbMa2ett1FY

[MT-2500]

Originally Posted by mcdon26

I've taken some videos to at least show what I'm talking about, the first video is to give some perspective on the pressure gauge dial as it's a little hard to video it close up while driving. Here is the link to the first video. you should be able to see the rest in my channel. Let me know if you cannot.

http://www.youtube.com/user/mcdon26?.../5/RbMa2ett1FY

Good pictures.

Looks like you have fuel pressure regulator and fuel pump problems both.

Bounching or Flopping gage indicates bad pump or wiring or voltage to it.

Block/plug return line or tap on direct to fuel filter in line and see what the pressure goes to.

Good strong pump should deliver 95-105 lbs. direct pressure.
Running on road regulated fuel pressure should run 62-64 lbs.

Drive it until it acts up or quites and then check pressure.
Post back fuel pressure when acting up or quits.

[MT-2500]

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 95-105 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 95-105 or more.
And if it has a fast leak down after shut off you have a leak in system.
Drive untill it quits or acts up.
And check fuel pressure then.
Post back fuel pressure readings.

[mcdon26]

Originally Posted by MT-2500

Good pictures.

Looks like you have fuel pressure regulator and fuel pump problems both.

Bounching or Flopping gage indicates bad pump or wiring or voltage to it.

Block/plug return line or tap on direct to fuel filter in line and see what the pressure goes to.

Good strong pump should deliver 95-105 lbs. direct pressure.
Running on road regulated fuel pressure should run 62-64 lbs.

Drive it until it acts up or quites and then check pressure.
Post back fuel pressure when acting up or quits.

Thank for the replies.

My leak down is not super fast, we're talking about 9 psi an hour I lose from shut off. Strangely enough, the hotter it got outside, the slower the pressure loss was. At one point I actually gained 2 psi. Here's what that break down looks like.

Turn off motor 42 PSI
1 hour check drop 9PSI to 33PSI
2nd hour check drop 9 psi 22PSI
3 hour check drop 3 psi to 19PSI
3.5 hour check up 1 psi to 20PSI
4 hour check up 1 psi to 21 PSI

At least you're confirming my thought I may have two issues, the question for me is which to fix first. I'm leaning towards the regulator, spider assembly (if I have one, I still haven't gotten confirmation yet.) and cpi nut kit. my thought is, if I'm getting adequate pressure to the fuel rail to stay running before I have this stall problem when hot, and my regulator/nut kit is leaking causing a flooding issue, a new fuel pump with higher pressure will make this problem worse. Or, I can just wait for this to happen again and see what that tells me.

I will have to locate the return line and attempt to pinch it off as suggested. Vice grips/pliers work? any recommendations on this?

Doesn't look like I will have any problems today because we never got to 80 and we have a storm coming in which has drop the temp considerably. Wednesday seems to be the high temp day so we'll see what happens then.

At least I feel like I'm getting somewhat closer to a resolution, just would hate to replace the fuel pump, and injector assemblies and still have the issue.

[MT-2500]

Originally Posted by mcdon26

Thank for the replies.

My leak down is not super fast, we're talking about 9 psi an hour I lose from shut off. Strangely enough, the hotter it got outside, the slower the pressure loss was. At one point I actually gained 2 psi. Here's what that break down looks like.

Turn off motor 42 PSI
1 hour check drop 9PSI to 33PSI
2nd hour check drop 9 psi 22PSI
3 hour check drop 3 psi to 19PSI
3.5 hour check up 1 psi to 20PSI
4 hour check up 1 psi to 21 PSI

At least you're confirming my thought I may have two issues, the question for me is which to fix first. I'm leaning towards the regulator, spider assembly (if I have one, I still haven't gotten confirmation yet.) and cpi nut kit. my thought is, if I'm getting adequate pressure to the fuel rail to stay running before I have this stall problem when hot, and my regulator/nut kit is leaking causing a flooding issue, a new fuel pump with higher pressure will make this problem worse. Or, I can just wait for this to happen again and see what that tells me.

I will have to locate the return line and attempt to pinch it off as suggested. Vice grips/pliers work? any recommendations on this?

Doesn't look like I will have any problems today because we never got to 80 and we have a storm coming in which has drop the temp considerably. Wednesday seems to be the high temp day so we'll see what happens then.

At least I feel like I'm getting somewhat closer to a resolution, just would hate to replace the fuel pump, and injector assemblies and still have the issue.

Pinch the rubber part of line.
Vise grips is a little hard on hose.
They make a special hose pinch tool or just plug return line.

IF FUEL PUMP DOES NOT MEET ALL PRESSURE SPECS AND TEST BETTER REPLACE IT.
And use A delphi pump.
Airtex and aftermarket pumps are junk.

Does you fuel lines go into top of engine or into rear intake?

[mcdon26]

fuel lines go into the back of the intake. That is where the schrader valve is.

[MT-2500]

Originally Posted by mcdon26

fuel lines go into the back of the intake. That is where the schrader valve is.

You have the nut kit set up then.
Another place for it to leak off fuel pressure.

[mcdon26]

Originally Posted by MT-2500

You have the nut kit set up then.
Another place for it to leak off fuel pressure.

which also means the spider assembly correct?

It's a shame because the motor was just replaced 3 weeks ago and the mechanics told me I needed to replace the injector O rings. They only charged me parts cost because the intake was apart. Wish I had known I would have had everything replaced.

GM dealer says I don't have the spider assembly but they call it a injector body kit. Runs about 150.00

[MT-2500]

Originally Posted by mcdon26

which also means the spider assembly correct?

It's a shame because the motor was just replaced 3 weeks ago and the mechanics told me I needed to replace the injector O rings. They only charged me parts cost because the intake was apart. Wish I had known I would have had everything replaced.

GM dealer says I don't have the spider assembly but they call it a injector body kit. Runs about 150.00

Strange I do not remember any injector O rings on that set up.
But a lot of pressure regulators leak on them.
Good luck.

[mcdon26]

I'm thinking they replaced O rings in the nut kit. The one at the dealer I saw had them. Looking for confirmation I do have the spider assembly though. The nut kit looks right just not sure of the spider assembly. Thinking if replacing both the fuel pump and regulator, assembly and nut kit all this weekend.

[maxisp2000]

Mcdon,
It's up to 90 degrees today in Las Vegas. I drove the car around from 2:00 to 4:00 with the scantool on, but not the fuel pressure gauge. The scantool reports fuel usage,
I was trying to get the car to fail. So I drove around through drive thrus, parking lots and side streets. Stopping and idling. Run the engine at 2000 rpm when parked. The coolant went up to 210 for most of the trip. I turned off the engine in parking lots, sat in traffic at lights ran 2-3 miles at a time and the car ran fine. I tried to get it to heat up and fail.
I sat at home in the driveway for 30 minutes at the end with full AC on and the car started 5 times no problem. Drove the circuit again with no problems.
Since I put another heatsink on the back of the existing ICM heatsink, using silver CPU paste in between, and moved it off the hot coil bracket mounted on the intake manifold, the car has not failed.

[mcdon26]

Originally Posted by maxisp2000

Mcdon,
It's up to 90 degrees today in Las Vegas. I drove the car around from 2:00 to 4:00 with the scantool on, but not the fuel pressure gauge. The scantool reports fuel usage,
I was trying to get the car to fail. So I drove around through drive thrus, parking lots and side streets. Stopping and idling. Run the engine at 2000 rpm when parked. The coolant went up to 210 for most of the trip. I turned off the engine in parking lots, sat in traffic at lights ran 2-3 miles at a time and the car ran fine. I tried to get it to heat up and fail.
I sat at home in the driveway for 30 minutes at the end with full AC on and the car started 5 times no problem. Drove the circuit again with no problems.
Since I put another heatsink on the back of the existing ICM heatsink, using silver CPU paste in between, and moved it off the hot coil bracket mounted on the intake manifold, the car has not failed.

Did you use a heatsink exactly like the original? and do you have pictures of your setup? how/where did you mount it? I know there are plenty of available places to connect up to, just curious of your setup. Glad to here it didn't fail for you today.