'99 Vortec power loss and CSFI questions

[D60]

My neighbor has a '99 Escalade with 199k on the clock. He reports occasional power loss, typically when climbing. Says if he pulls off the road it sometimes surges and idles poorly. Stalled once.

He says sitting for 5 minutes and restarting solves the issue. Allegedly fuel filter replaced recently.

No codes. No misfire codes. No pending codes.

Typically I'd think fuel pump here. Will put a gauge on it.

However apparently the poppet style CSFI can also cause similar symptoms?

If it were the CSFI, would you expect to typically see misfire codes?? Or can you see power loss across the board with no individual cylinder called out? And if it were the CSFI, would a 5 minute "timeout" clear the symptoms?

 

[fantastic]

My neighbor has a '99 Escalade with 199k on the clock. He reports occasional power loss, typically when climbing. Says if he pulls off the road it sometimes surges and idles poorly. Stalled once.

He says sitting for 5 minutes and restarting solves the issue. Allegedly fuel filter replaced recently.

No codes. No misfire codes. No pending codes.

Typically I'd think fuel pump here. Will put a gauge on it.

However apparently the poppet style CSFI can also cause similar symptoms?

If it were the CSFI, would you expect to typically see misfire codes?? Or can you see power loss across the board with no individual cylinder called out? And if it were the CSFI, would a 5 minute "timeout" clear the symptoms?

I believe this was one of the years that suffered the poppet valve injector issues. 20 yrs ago I had 1 s10 blazers 1999 that suffered this fate. But with the surging idle it could be Idle control sensor. Also, I think a fuel pump would be in order if it's original.

 

[clinebarger]

Be aware of tight valve guides causing misfires during & after hard acceleration, Known issue with Vortec 5.0L/5.7L's.

However.....Verifying fuel pressure is a good a place as any to start. I got in the habit of "Dead Heading" these pumps to check their health, A good pump will produce 90-100 PSI.

Sticky Poppets will usually cause hard start concerns when cold, A good cleaning with Top Engine Cleaner will usually....At least temporarily solve the issue. I'm all for a MPI conversion (Updated Spider) though!!!

I'd be surprised if the Distributor didn't have play &/or a worn drive gear at 200,000.

I've seen aftermarket Crank Sensors hit the Reluctor Wheel & cause strange drivability issues, I've seen this set DTC's & not set DTC's.

The Cam-Crank Offset PID can be useful.....If it freaks out & goes way Positive or Negative off idle....You have an issue with either the Crank Sensor hitting the Reluctor or the Distributor is worn.

Misfire Cycle PID is also useful....If it's not counting up....The Misfire Monitor is offline.

 

[D60]

Be aware of tight valve guides causing misfires during & after hard acceleration, Known issue with Vortec 5.0L/5.7L's.

However.....Verifying fuel pressure is a good a place as any to start. I got in the habit of "Dead Heading" these pumps to check their health, A good pump will produce 90-100 PSI.

Sticky Poppets will usually cause hard start concerns when cold, A good cleaning with Top Engine Cleaner will usually....At least temporarily solve the issue. I'm all for a MPI conversion (Updated Spider) though!!!

I'd be surprised if the Distributor didn't have play &/or a worn drive gear at 200,000.

I've seen aftermarket Crank Sensors hit the Reluctor Wheel & cause strange drivability issues, I've seen this set DTC's & not set DTC's.

The Cam-Crank Offset PID can be useful.....If it freaks out & goes way Positive or Negative off idle....You have an issue with either the Crank Sensor hitting the Reluctor or the Distributor is worn.

Misfire Cycle PID is also useful....If it's not counting up....The Misfire Monitor is offline.

Thank you. How do you dead head the pumps?

What do you reco for top end cleaning? He does report recent hard starting when cold.

 

[clinebarger]

Thank you. How do you dead head the pumps?

What do you reco for top end cleaning? He does report recent hard starting when cold.

Edelmann 24003 16mm O-ring Fitting, Remove the front/forward line off the fuel filter, Screw in the 24003 with some 300 psi fuel injection hose adapted to your FP gauge, Bleed the air out by pulsing the FP Relay a couple times while depressing the bleed , Run the pump @ 10 seconds.

My Cornwell master FP set has 16mm adapters.

Top Engine Cleaner is "HOT" & will destroy a fuel pump, I use a regulated air powered pressure vessel, Before coming across the Snap-on one I have now, HERE. I had a modified paint pressure pot.

I modified a factory L31 intake fuel pipe assembly, I'll snap some pic's tomorrow.

 

[D60]

Thank you again @clinebarger

How do you feel about the Seafoam setup you slip into the intake? Unlikely to help? Potentially harmful?

edit: I guess that doesn't make its way through injectors, so not what we're aiming for

 

[clinebarger]

Here's a pic of the modified intake fuel pipe, I bent it "Up" to where I can just move the existing lines out of the way, You have to remove the 10mm headed hold down bolt to have enough wiggle room to move it out of the way.

The reason I do this.....I like to run the pressure up to around 75 PSI & you don't want the regulator to return all the cleaner back to the tank.

 

[mattd]

Be aware of tight valve guides causing misfires during & after hard acceleration, Known issue with Vortec 5.0L/5.7L

This. My father in laws old 4.3 had the same issue. Almost since new and slowly got worse. Pulled the heads and did Valve job and no more issues.

 

[D60]

This. My father in laws old 4.3 had the same issue. Almost since new and slowly got worse. Pulled the heads and did Valve job and no more issues.

Did you get codes set for misfire? Or does the PCM not pick up on it?

We have no codes in this instance

 

[mattd]

Did you get codes set for misfire? Or does the PCM not pick up on it?

We have no codes in this instance

It would set a P0300 some times that’s it. Looking at individual cylinder misfire counts did help but nothing was glaring. It would only do it pulling his trailer up hill or climbing a long grade. Under mid range RPM.

 

[clinebarger]

Did you get codes set for misfire? Or does the PCM not pick up on it?

We have no codes in this instance

Gen 1 Vortec's have a 4x crank reluctor.....Not a lot of resolution to work with. Gen III LS engines uses 24X & Gen IV & V uses 58X.

 

[D60]

Edelmann 24003 16mm O-ring Fitting, Remove the front/forward line off the fuel filter, Screw in the 24003 with some 300 psi fuel injection hose adapted to your FP gauge, Bleed the air out by pulsing the FP Relay a couple times while depressing the bleed , Run the pump @ 10 seconds.

My Cornwell master FP set has 16mm adapters.

Top Engine Cleaner is "HOT" & will destroy a fuel pump, I use a regulated air powered pressure vessel, Before coming across the Snap-on one I have now, HERE. I had a modified paint pressure pot.

I modified a factory L31 intake fuel pipe assembly, I'll snap some pic's tomorrow.

Revisiting this, I get 80 psi when dead-heading at the filter (bled air out). Would you say that's likely healthy?

I was able to cobble this together with an SUR&R 16mm adapter

Also, for those who don't know (I didn't), GM uses relays that look like "large" relays but are pinned like the small rectangulars, thus this bypass relay will work. GM appears to also employ an 87a -- I wonder what the second output feeds (just curious)?

 

[clinebarger]

Revisiting this, I get 80 psi when dead-heading at the filter (bled air out). Would you say that's likely healthy?

I was able to cobble this together with an SUR&R 16mm adapter View attachment 214861

Also, for those who don't know (I didn't), GM uses relays that look like "large" relays but are pinned like the small rectangulars, thus this bypass relay will work. GM appears to also employ an 87a -- I wonder what the second output feeds (just curious)?View attachment 214862

Marginal at best, I like to see 95-100 PSI.

87A is for the "Fuel Pump Prime Connector", You've probably seen a taped down red wire & a Packard 56 series female spade connector near the fuse box....Which is likely the only Packard 56 series connector used on a late GMT400's.

Used to prime the fuel system or drain the tank with a fused jumper.

 

[D60]

Marginal at best, I like to see 95-100 PSI.

87A is for the "Fuel Pump Prime Connector", You've probably seen a taped down red wire & a Packard 56 series female spade connector near the fuse box....Which is likely the only Packard 56 series connector used on a late GMT400's.

Used to prime the fuel system or drain the tank with a fused jumper.

Thank you. I also found when using the top end cleaner it wouldn't run until ~50psi. I figure this has to do with sufficient pressure for the poppets?

I was trying to stay under the FPR as I didn't block off the return line.

ANYWAY, it made me realize this system should be more susceptible to stumbling or stalling with a weak fuel pump if it essentially has a distinctive go/no-go pressure....assuming I'm understanding correctly

 

[Nick1994]

I had that with my '96 Chevy pickup. Had a bad connection at the fuel pump relay

 

[Lawnman23]

Thank you. I also found when using the top end cleaner it wouldn't run until ~50psi. I figure this has to do with sufficient pressure for the poppets?

I was trying to stay under the FPR as I didn't block off the return line.

ANYWAY, it made me realize this system should be more susceptible to stumbling or stalling with a weak fuel pump if it essentially has a distinctive go/no-go pressure....assuming I'm understanding correctly

With the key on, engine off you should be seeing 60 - 65psi at the test port on the line. The FPR is bleeding off any additional pressure back to the tank. While running, you should optimally be seeing 55+ psi. The poppets wont open/engine wont start if pressure is under 50psi. You can always attach the fuel pressure gauge and tape it to the windshield and go for a drive to observe FP under load.

This site has a good diagnostic procedure to follow to test the injector assembly and the fuel pump itself.

I've replaced the fuel pump on my 98 twice and replaced the poppet assembly with the upgraded Multec 2 injector assembly when I had the intake off to replace lower intake gaskets. Fun times.

 

[D60]

With the key on, engine off you should be seeing 60 - 65psi at the test port on the line. The FPR is bleeding off any additional pressure back to the tank. While running, you should optimally be seeing 55+ psi. The poppets wont open/engine wont start if pressure is under 50psi. You can always attach the fuel pressure gauge and tape it to the windshield and go for a drive to observe FP under load.

This site has a good diagnostic procedure to follow to test the injector assembly and the fuel pump itself.

I've replaced the fuel pump on my 98 twice and replaced the poppet assembly with the upgraded Multec II injector assembly when I had the intake off to replace lower intake gaskets. Fun times.

Sure, but clinebarger's approach makes sense to me. Without dead-heading the pump the FPR is blinding one to the pump's ultimate capability. It might only be capable of 66psi but if the FPR won't let you see more than 65, you just don't know.

I was seeing around~53 running, but when we start splitting hairs over 2psi I begin to question the accuracy of each respective gauge. I imagine most of these analog gauges are +/- 2 psi no matter what the manufacturer says.

Point being, I think pressure under normal conditions is fine. But if clinebarger says 80 max is marginal, I believe him. It'd be nice to be standing there with a gauge on the fuel rail when the owner experiences the problem (primarily during or after climbs), but that's hardly realistic unfortunately

 

[Lawnman23]

Sure, but clinebarger's approach makes sense to me. Without dead-heading the pump the FPR is blinding one to the pump's ultimate capability. It might only be capable of 66psi but if the FPR won't let you see more than 65, you just don't know.

I was seeing around~53 running, but when we start splitting hairs over 2psi I begin to question the accuracy of each respective gauge. I imagine most of these analog gauges are +/- 2 psi no matter what the manufacturer says.

Point being, I think pressure under normal conditions is fine. But if clinebarger says 80 max is marginal, I believe him. It'd be nice to be standing there with a gauge on the fuel rail when the owner experiences the problem (primarily during or after climbs), but that's hardly realistic unfortunately

Yep, I understand what he's saying.

My point was the need to verify if its the pump itself that's weak or if the FPR under the plenum is bad and bleeding off the pressure. The hard cold starts in the morning can be a result of either, or both for that matter.

Any idea how old the pump is? At 199k I would have to think its already been replaced at least once.

 

[D60]

Yep, I understand what he's saying.

My point was the need to verify if its the pump itself that's weak or if the FPR under the plenum is bad and bleeding off the pressure. The hard cold starts in the morning can be a result of either, or both for that matter.

Any idea how old the pump is? At 199k I would have to think its already been replaced at least once.

We don't have much history on the truck. The current owner has had it since ~2017 and never had the pump replaced, but that's all we know. I'm not sure of mileage when he purchased it.

The hard starts in the morning he can live with (he's been cycling the key like I showed him), but I'd like to reduce his chances of power loss and stalling.

 

[D60]

I replaced the pump yesterday with GM Genuine, complete with their fancy blue GM tape -- I almost feel like I'm breaking the law opening the box!

Anyway, not much useful info because I didn't have time to dead head the new pump.

The existing pump was a Carter, so yeah, it's been done before. But judging by the amount of rusty dirt on top of the tank, it's been a long time.

I know it's not an accurate indicator of pump health, but when the pump primes it's virtually silent. The old Carter had a distinct whine. On initial start I thought I had somehow screwed up wiring the provided 4-flat replacement electrical connector, but no -- it's just really quiet