6.5 w/mechanical pump won't shut off

[DP]

I've had this happen occasionally over the last year or so. This morning it got real serious. Unplugged everything I could reach on the IP, unplugged the oil pressure switch (hoping to kill the lift pump), even unplugged the lift pump. No dice. Finally put a pair of vicegrips on the feed line to the filter, put it in gear and it died in a couple of seconds.
All my manuals are at home so I can troubleshoot tonight but I was wondering if anyone has run into this before.
'93 C2500 8600GVW w/mechanical pump.
Thanks in advance.
Dave

[convert2diesel]

Siezed fuel shut-off solinoid. Replace and then start using lubricant in the fuel. The next time (if there is a next time) just pinch off the fuel return line. The increase in dome pressure will retard the timing till it stops.

Bill

[DP]

Thanks for the info. Where on the pump is the solenoid located? I knew it had to have some kind of plunger or solenoid or something, but nothing looks obvious on the pump. Even googling stuff this morning, I haven't found any hit for "shut-off".
Thanks again.

[DmaxMaverick]

Sounds like the solenoid is seizing or the internal linkage is damaged/worn.

Once the fuel pump is disconnected/depowered, you can open the filter bleed or drain valve to kill the engine. Pinching lines is OK in a pinch, but will cause the line to fail after a few times, and quicker if it's older.

[Robyn]

The fuel shut off on the DB2 is not really a fussy little critter. Usually the issue will be that the solenoid will fail and the rig shuts off or that they wont start after being shut off.

Does this rig have a lot of miles on it??

The DB2 is very forgiving, other than dirty fuel.
The shut off solenoid is an electric device that actuates the fuel control valve and allows it to completely stop fuel flow.

Possibly the linkage has become worn, the solenoid itself is seeing the armature swell and then after becoming warm from use is sticking.

Sounds like its time to get the IP off and into the shop for a good looking over.

You can remove the top of the IP and do some checking for issues and possibly all it needs is a new solenoid.

Best

Robyn

[DP]

The truck has about 210K on it and has never had any engine related problems. Where is the solenoid located? I see an external one that looks like a fast idle, it's just got a plunger that pushes on the throttle arm. I did find some pics online of a new shut-off solenoid and it looks like it screws into the pump body somewhere. Remember this is a mechanical pump.
Thanks for the input.
Dave

[DmaxMaverick]

[edit] The solenoid is under a cover at the front/top of the pump. Be very careful on assembly (and pay close attention or take some pics during disassembly), especially with the linkage. Improper assembly can/will result in what you are seeing now.

If you can still duplicate the no-shut-off condition, try "tapping" the solenoid cover with a wrench or something (don't hammer it, or hit it hard enough to dent the cover). If the solenoid is just stuck, you should be able to free it with light tapping. If it works (engine stops), then only the solenoid should need replacement. The pump does not need to be removed from the engine for solenoid replacement.

[DP]

OK. Since the filter housing was empty anyway I went out at lunch to swap the fuel filter and have a closer look at the IP. The only cylindrical thing on the top is an external solenoid mounted on the drivers side at about 30 deg from horizontal. This is the one that looks like a fast idle can off a Qjet. It has a plunger pushing on the throttle arm and a single green 18g wire on the back.
On the top passenger side, an insulated lug coming straight up has a single red 14g wire attached. There is a matching grounded lug on the drivers side, grounded to the pump.
Coming out of the passenger side, right above the output shaft for the TPS, is a lug with a green 14g wire.
Then below that is the TPS for the transmission.
The pictures that I've found for a shut-off solenoid like this one:
http://us.st12.yimg.com/us.st.yimg.com/I/yhst-33052174269936_2015_2033619
look nothing like what I can find on my pump.
So... is the shut-off solenoid somewhere else, like the bottom, or what does it look like.
Help! Thanks.

[DP]

Dmax,
Thanks for your help, but I still don't see anything that looks right. Don't know how to post pics here so I sent you an email with a pic of the top of the pump. I think the solenoid has to be under the cover with the red wire going to it.
Thanks again.

[DmaxMaverick]

My mistake. I was describing a DS pump (electronic). Posts were corrected. Symptoms and cure are the same, though.

[DP]

Cool.. Thanks to all for your input today. I'm going to do a WVO conversion on this truck starting next week, so I'll replace the solenoid when the intake is off.
Thanks again.
Dave

[convert2diesel]

DP:

You should have two wires going into the top of the pump on the passenger side. The one at the front is the one for the fuel shut-off. There is no solinoids outside of the pump other then the fast idle plunger. Both the fuel shut-off and the HPCA are inside the dome. Don't have to remove the intake to get access. Just three small bolts hold the dome on and they are accessable from the top. Be careful when replacing the dome as it is very possible to re-install it wrong, forcing the rack to the wide open position. Makes for an interesting first start :eek:.

Do some real soul searching before you commit to WVO. I use home brew bio-diesel and have had very few problems but the guys that run the straight stuff have reported a miriad of issues including snapping the pump shaft. A few have been successful but for the most part, they have been very anal about oil quality, filtering, de-watering and temperatures. These pumps are not very tolerant of heavy fuels.

Robyn: I have encountered this problem a few times, especially since we went to ULSD here in Canada. The fuel solinoid hangs up in it's bore and fails to return. Just a little lubrication is all that is needed most of the time. Even had a new solinoid hang up on me so it is not really indicative of a worn pump. As far as the return line trick, I would doubt the pressure needed to bog out the engine would exceed 10 PSI. I just use a pair of needle nose pliers on the top flex line.

Bill

[DP]

Thanks again to all that posted info. I was out of town this weekend so didn't get back to it until yesterday afternoon. Looks like the reason the solenoid is hanging up is because some material from the coil is breaking down and getting wedged between the coil and the plunger. While energizing/de-energizing the solenoid, I see small metallic bits coming out of some of the seams as the magnet turns on and off. I'm picking up a new one today.
Bill, I appreciate your comments about the WVO. I've also talked to one person that sheared a pump shaft. I think that some if not most of the problems that people run into is taking too casual of an approach to doing the conversion. The guy I talked to suspects he sheared is shaft because of too much pressure from the lift pump. Turns out he was running about 14-16 psi. The spec is like 5-8 psi. A lot of people seem pretty casual about getting the oil good and hot as well. I'm going ahead with the conversion but will tread lightly. Since I don't have a large enough weekly supply of WVO, I'll likely never run it straight. It will probably be something like 60-75% WVO, straight diesel of course for start up and shut down.