Resolved: Miss and Skip under light throttle

[GreenGiant]

In the year 2000, I posted to one of the forums here regarding a miss that my 98 K3500 was having under light throttle.

I described it then as a hickup or sharp but small lurch when cresting a grade or descending a very slight grade. It would happen frequently but randomly under those conditions.

For everyone's benefit, I'll now describe the resolution.

In short, the problem was the fuel selenoid ( not the FSD ), the selenoid itself was sticking part way through the close or the subsequent open operation. When the problem got bad enough, it set both the open and close trouble codes.

A replacement pump under the extended warranty resolved the issue.

[More Power]

Thanks for the update.

MP

[CareyWeber]

Originally posted by GreenGiant:
In the year 2000, I posted to one of the forums here regarding a miss that my 98 K3500 was having under light throttle.

I described it then as a hickup or sharp but small lurch when cresting a grade or descending a very slight grade. It would happen frequently but randomly under those conditions.

For everyone's benefit, I'll now describe the resolution.

In short, the problem was the fuel selenoid ( not the FSD ), the selenoid itself was sticking part way through the close or the subsequent open operation. When the problem got bad enough, it set both the open and close trouble codes.

A replacement pump under the extended warranty resolved the issue. GreenGiant,

Do you mean the fuel shutoff solenoid?

Do you know what codes were set?

Carey

[GreenGiant]

In the injection pump is a selenoid that controls the inject event. That selenoid is what the FSD drives.

The FSD monitors the action of that selenoid electronically to determine how long it takes to respond.

P1216 - Fuel Selenoid Response Time Too Short
P1217 - Fuel Selenoid Response Time Too Long

P1216 sets when the closure is less than .75 ms
P1217 sets when the closure is more than 2.5 ms

Where both set. Both indicate a sticky or mechanically failed selenoid.

You can imagine the chaos that can cause under light throttle settings because it would result in too little fuel.

Curiously, I was also having troubles with the cruise control disengageing all by itself at seemingly random periods. That problem went away too. These are type D DTCs so I'm guessing the computer would turn off cruise control when this happened too and that not every occurence resulted in a noticeable miss.

-James

[rjwest]

That is what failed in my pump, Took a year to to the point where it started causing " shut down's"

Only 1 time did I get a code...

[Jim H.]

Thanks for the information, mine has been doing the same thing for a while. The cruise control symptom is a little different, sometimes it "loses" its memory and won't resume. I was beginning to suspect the computer but you message, along with others that have had similar problems have convinced me to put the pressure on GM to get the dealer to replace the pump.

[tom.mcinerney]

Thanks, G~G~.
GreenGiants' report is consistent with the advice given Damork by a Stanadyne pump rebuilder-- namely, that the fuel solenoids fail routinely, and that a good portion of FSD failures result from solenoids which don't move smoothly.

Clean, lubed fuel helps.

[DKeen]

Mine just started this over the past week. I have the remote FSD, so I was not sure what it was. It started right after I filled up with new fuel. Can this solenoid be replaced without replacing the pump?

[GreenGiant]

I'll validate your experience Jim H.

As I recall, when the cruise control disengaged I could not get it to resume either until I turned it off and back on. I've been blessedly free of this issue for a year now so the details are starting to get little fuzzy.


GreenGiant

[GreenGiant]

I think you'd have to get as far as taking the pump off just to get at the solenoid.

[gmctd]

Replacement requires adjustment on a Bacharach or equiv flow machine to get proper response time setup - Stanadyne service centers, only.

[DaveHart]

Somebody please give me the short version to fix. I think this one nailed my problems on the head. Been doing it since purchased.

[65turboman]

Sometimes I notice the cruise control problem(not setting or resuming and a steady SES light for about 10 seconds). Today, just after restart in a parking lot the engine died. I turned off the key and tried to restart, but it just repeatedly cranked. After the second try to start, it fired up and ran normally. Sounds like the same problem, however I wonder if the PMD (still mounted on the pump) could be going bad.
______________________________________
1995 Chevy Reg. Cab 2500HD 6.5TD

[rjwest]

Without the ability to swap the FSD you will not be able to tell if pump or fsd is bad

If no codes and out of warrenty, I would suggest getting a remote mount mount fsd, Try tightning screws, or replace fsd , Than probably replace
IP if still failing.


Suggest you read all old posts, as there are many
other problems that can cause stalling.

I had 1 code during a year of troubles.( inj pulse to short ). During that time,2 bad FSD's ( 1 on intake mount and 1 on pump ) Finially after " Eng Quites/restarts" and imediate swap of FSD with same problem occuring within 10 minutes.
I called GOMER'S, they said, definetly pump, they were right.

[Reinman]

I battled with similar "miss and skips" under light throttle which eventuall developed into outright stalls as if someone shut off the ignition (symptom of faulty FSD) DTC's after stall pointed to faulty fuel sylenoid as discribed in previous posts. As it turns out, my problem was a bad connection at the optical/fuel tempture sensor, located directly on top of the injection pump at the front. I squeezed the connectors down to tighten them and on subsequent start up codes went away along with the problem. Moral of the story: make sure your connections are good before you spend the money on a new IP.

[Marty Lau]

Green Gaint;

Do you have a part number for the Fuel Solenoid?
Where did you get it?
Thanks
16ga

[Huntgfish]

I have been having the same symtoms, and as I think back, before I bought it from my dad, he told me that at least two times he has forgot and filled up with gas, and tried to keep the tank full of diesel until he thought it burned down. Which seems like that in itself could cause all the problems I have been seeing with my fsd and ip having the same side effects. Any thoughts?

[Marty Lau]

I changed the OPS last night and it seems to have solved my problem. I'll post more at the current OPS thread.