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Need some input....

HighSierra86

HighSierra86

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Location
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Ok guys, I need some help here. We have a 2000 chevy express van with the 6.5. Yesterday it started acting up and im having some trouble figuring out what is going on.

One of our guys was out on the road and it went into limp mode with an SES light. Limped it back to the yard where I got to look at it. Found code P0251 in the system. I took it for a ride to check that it was in limp mode...it started and idled fine but as i started driving the RPMs suddenly raced up like my foot was to the floor. I dropped it into neutral and coasted to a stop, where it shut off shortly after. It restarted right away and i drove it back to the yard.

I checked fuel pressure and found none at the t-valve (or in this case a pressure tap? must be a newer model thing for a quick disconect guage). Found I had power at the lift pump but no pumping.

Replaced the lift pump with a new 93' model. Van started right up, with a nice smooth idle. But now, any increase in throttle leads to a large surge in RPMs. With the pedal in any position over idle, the RPMs will hunt up and down consistantly, in drive or in park. :confused5:

This truck is on the original IP at 130K miles. PMD has been relocated with a heath unit behind the bumper last fall. Mind you that exact unit has been on 3 other trucks over the last few years, but never any issues.

The only other clue I have is last year (before the PMD replacement) I had it throw the P0251 code again and go into limp mode. I cleared it, and nothing came back until now.

Any tips or hints would be greatly appreciated..I was wondering if it would be worth it to swap in another optic sensor? Everything, and I mean everything on this truck is a royal PITA to get to due to the engine being stuffed under the dashboard. Thanks for any help guys

-Nick
 
Hunting and large surges in RPM would tell me the fuel solenoid armature in the IP is shot/busted. The real give away is the engine racing up real high when you barely touched the throttle. When the fuel solenoid armature breaks you basically end up with 2 throttle positions, idle and ridiculous.

The P0251 code is an optic sensor code. It's usually coupled with a P0370.

When my optic sensor ended up dead to the world it would start like crap(lots of coughing/smoking/hunting before it smoothed out), ran at very reduced power, and had an SES light with P0251/P0370. Even stalled sometimes. That doesn't sound like your problem though. I still had full throttle control during all this.
 
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iamdave0887 said:
Hunting and large surges in RPM would tell me the fuel solenoid armature in the IP is shot/busted. The real give away is the engine racing up real high when you barely touched the throttle. When the fuel solenoid armature breaks you basically end up with 2 throttle positions, idle and ridiculous.
Click to expand...

X2
 
iamdave0887 said:
Hunting and large surges in RPM would tell me the fuel solenoid armature in the IP is shot/busted. The real give away is the engine racing up real high when you barely touched the throttle. When the fuel solenoid armature breaks you basically end up with 2 throttle positions, idle and ridiculous.

The P0251 code is an optic sensor code. It's usually coupled with a P0370.

When my optic sensor ended up dead to the world it would start like crap(lots of coughing/smoking/hunting before it smoothed out), ran at very reduced power, and had an SES light with P0251/P0370. Even stalled sometimes. That doesn't sound like your problem though. I still had full throttle control during all this.
Click to expand...

X3. IPs usually go out about 120K to 130K miles.
 
Try new pmd.
Blow out the lines
Sounds exactly like what my dirty fuel sock did.
 
OK so a little update. Let the van sit overnight and then this morning I went out to restart. Started and idled as normal. I then proceded to drive around for about half an hour with almost zero issues. Ran great.

The only thing abnormal I noticed was after full throttle runs if you let off quick, the RPMs will surge back up again quick. But only for a second or two. Otherwise no issues. Im probably just going to keep the truck on the road again until something else pops up. With the amount of money we have spent on this truck in the last 4 years I really dont want to keep dumping more in. Even though I will, because buying something newer isnt an option in this economy...

Anyways, hoping the new fuel pump will straighten out some of the issues and codes. My only thought was there may have been air in the lines after I changed the pump, and maybe somehow it worked its way out overnight?? Dont know where it would have released through but I dont know how else to explain that. The joy of electronics.

-Nick
 
The P0251 code is an optic sensor code. It's usually coupled with a P0370.

When my optic sensor ended up dead to the world it would start like crap(lots of coughing/smoking/hunting before it smoothed out), ran at very reduced power, and had an SES light with P0251/P0370. Even stalled sometimes. That doesn't sound like your problem though. I still had full throttle control during all this.
Click to expand...

Just got these 2 codes yesterday.....I cleared the codes, dumped a qt. of SAE30 ND oil and a 8oz bottle of Standyne conditioner in and codes havn't come back yet......That said I do experience the "messy" cold starts but I can clear it up with a tap to the go pedal.....and power in general is about what I'd expect for a 10,000 lb 6.5 with stock programming....Whaddayathink?......Add an optic sensor to the list, and if so where should I pick one up?

FWIW, this was after running 2 tanks of fuel that was untreated.......Also while on the fuel subject I spoke to a Hess rep the other day (for fuel cards...for the drivers) and the rep said the ULSD (Ultra low sulfer diesel) deal has been shown to be a real problem for the older diesels, as we all know.......She pointed out that the Federal minimum of sulfer is 20PPM and the highest is 40PPM, Hess is the only one of the "big stations" that are pumping 40PPM and also adding a "Cheap" (Her words) fuel conditioner to service their cutomers and is used as a "Sales pitch" (my words) to sign up potential customers.

Just thought my fellow "Dinosaur Diesel" brothers would find this info interesting.....I'm not sure how much a difference the 20 to 40PPM difference makes, but I figure we can use as much sulfer as we can get.

Anyone know the "Old" PPM of sulfer was in the LSD (Low sulfer diesel) and the regular diesel?


SORRY for the Hijack, Nick
 
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Well I'm gonna go with dirty gnd's 1st as that is free to check ALL of them,

Then FSD/PMD which is still IP mounted Y/N ??????,

We don't know how long lift pump was out but remember full fuel supply to IP is critical for making power but also lube for IP innards and coolant for the IP mounted driver.

If driver was remoted in a previous life, was it remoted when new or after it had been on a IP in a previous life ergo a "used but good driver" at time of relocation. Once it has been mounted on an IP or anywhere under the hood for that matter it is suspect; and IMO only good for a spare beyond that point.

Adding oil to fuel mix will help some with worn innard parts but if that is case start putting away some coins as that is a band-aid to a IP that is showing its age, 120-130 k with today's low lubricity fuels is not a given it is going to fail, but not helping the situation either always-always-always run with a fuel additive or oil to your mix.

I'd recommend also the 2000 rpm test as well as if it fails that another indication fuel metering solenoid on end of the IP is on it's way out
 
Good point about the grounds. I've not heard of grounding issues causing engine to race though. I'm putting money on the PMD.
Nick, What band PMD are you running
 
Brooklyn Tow said:
Just got these 2 codes yesterday.....I cleared the codes, dumped a qt. of SAE30 ND oil and a 8oz bottle of Standyne conditioner in and codes havn't come back yet......That said I do experience the "messy" cold starts but I can clear it up with a tap to the go pedal.....and power in general is about what I'd expect for a 10,000 lb 6.5 with stock programming....Whaddayathink?......Add an optic sensor to the list, and if so where should I pick one up?

FWIW, this was after running 2 tanks of fuel that was untreated.......Also while on the fuel subject I spoke to a Hess rep the other day (for fuel cards...for the drivers) and the rep said the ULSD (Ultra low sulfer diesel) deal has been shown to be a real problem for the older diesels, as we all know.......She pointed out that the Federal minimum of sulfer is 20PPM and the highest is 40PPM, Hess is the only one of the "big stations" that are pumping 40PPM and also adding a "Cheap" (Her words) fuel conditioner to service their cutomers and is used as a "Sales pitch" (my words) to sign up potential customers.

Just thought my fellow "Dinosaur Diesel" brothers would find this info interesting.....I'm not sure how much a difference the 20 to 40PPM difference makes, but I figure we can use as much sulfer as we can get.

Anyone know the "Old" PPM of sulfer was in the LSD (Low sulfer diesel) and the regular diesel?


SORRY for the Hijack, Nick
Click to expand...

Louis,

The old LSD was 500 ppm maximum. The really old regular "diesel" i don't think really had a PPM limit. Either that or i'm too young to remember. Hell i was 3 when the 1980s ended, unfortunately. My K-5 is older than i am. :hihi:
 
I'm thinkin along the line of TD, If that IP been runnin awhile with no LP....Try the 2 stroke trick. On the other hand Heath PMD's can fail. Mine did. Try it on something else if you can. I got a spare PMD if you wanna borrow it for testing.
 
Louis....Hijack away. No hurt feelings here. In regards to your fuel comment...This van runs untreated fuel in every tank. With so many different drivers I would never be able to keep an eye on who is fueling up the truck and if they are adding the correct amount of additive. With the small percentage of people who care enough to treat the fuel in every tank, I would expect to see more fuel related problems across the board then we actually do. That being said, my 96 gets stanadyne additive with every fuel up...my baby :hihi:

The van is currently on its 3rd PMD. All the previous ones I had mounted back on the pump, but this one came with heath's kit. Its either a d-tech or stanadyne, cant remember which.

As for grounds...really is worth a check. Last time I had the big dog house cover in the cab off, I cleaned what I could reach, but this thing is a bastard to work on. Makes me really appreciate all my conventional trucks.

Kenny, thanks for the offer. Ive been thinking of picking up a few good PMD spares myself for just such occasions. I did re-fuel with a double dose of fuel additive and so far so good. I drove it around personally yesterday for about 20 or so miles with no issues, and the guys have been running it up and down I95 all day today.

Im leaving for VT on sunday, first semi-vacation all year, so I hope it behaves its self while I am gone. Thanks again for the replies guys...more ideas I have the better

-Nick
 
I'd throw a qt of SAE30 in there also....It definitely can't hurt.

Enjoy the vacation.:chillpill::partay:...Trust me I know what its like to not be able to get away.

I'm WAY overdue for a little R and R myself. :auto:

:shots: :mikelsheep:
 
Do the grounds and blow back through the tank sock, neither costs any money. Then check if you have LP flow.
 
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