Problem with Bosch VE pump on 4BT....

[JimmieD]

This is a real problem, not just missing fuel ha haha!

On my 4BT with Bosch VE pump the truck runs fine but has a starting problem. When I pulled the motor and fuel tank from donor truck that truck ran and started perfectly. I used a solid steel line with no compression fittings for main fuel line, and fuel injection hose at either end for flex to tank and lift pump. Same with return line. I used donor truck's 26 gal aluminum tank. Blew out all lines. I installed a new Fleetguard FS1221 fuel filter. Engine was not run for 2-3 months but everything was sealed during that time.

I have completely bled all parts of the fuel system. The truck will not start unless the pressurized line coming from lift pump outlet, where it enters front of VE pump, is cracked open while cranking! Bleeding fuel filter banjo fittings has no effect.

I have now removed the F/I rubber hose and replaced with clear vinyl flex lines at both ends of fuel line. Bled it out and now have no air bubbles showing in line, no air from tank. No apparent leaks at fuel filter, filter banjo fittings or lift pump. I installed a NEW lift pump but no change, and it did precisely the same thing with the old lift pump after engine was swapped [but not before!]. I removed FS1221 fuel filter and checked gasket and mating surface. Tightened threaded filter attachment tube. There's an additional flat rubber gasket about 1/4 thick that's on that threaded tube which is hardened with no sign of coontact with filter or housing. The FS1221 is the spec filter for this engine.

What has me stumped is that only when I RELIEVE pressure going into VE pump will the truck start, and then instantly! Sometimes I get a little air bubbles when fitting is cracked, other times not. To repeat, the very instant that I crack that fitting at pump the truck instantly starts and runs perfectly. No apparent leaks. Thoroughly stumped here....

[Charles Talbert]

Boogers to find

It's quite obvious you have a small amount of air entering the system causing loss of prime at the pump. This could be in your plumbing or could be something internal in the injector pump. All I can say is check & double check till all avenues are exhausted, you may wind up having the pump built before you conquer the problem. The VE pumps were known for nickel/dime problems, a big reason Cummins went with the in-line pumps on later models. Any type of restriction in the return line to the tank can cause the problem also, most of the time that will result in a loss of power as if it is running out of fuel, but can also cause the cranking problem. Good luck.

[JimmieD]

Thanks much, charles, and I think you're on to it. Unless the banjo fittings are leaking, which were undisturbed for install, then it must either be air entering or excess pressures preventing fuel return from pump to tank. I have really been through the pressure side and feel confident there are ni leaks there.

However the return side is something I haven't invetigated deeply. We've got some critters around here that enter any small hole they and daub up a nest for their hatchlings. Could be.....? Also I was much more intent on fuel delivery and building 100% there, so maybe I need to check that return line again or completely re-plumb it.

It does not seem to be bleeding that it needs as much as a REDUCTION in pressure to the VE Rotary Vane Bosch pump. So, you're most likely correct on a faulty return line causing excess pressures in the pump inlet or case and that's what is relieved by cracking that fitting! I'll know by tonite.

You know, you're always pretty good at this stuff. You ought to give some serious thought to maybe doing it for a living or something? Just a thought....

[DThibault]

I just had a similar problem with a 6bt and VE, on a 91 Dodge. If you don't see fuel leaking from the VE when its running and it runs good after starting its not likely there is any trouble with that. I had the weirdest thing going on. I could get my truck started by bleeding the injectors and other places along the way from the lift pump (diaphragm) and it would run great. If I shut it off and restarted, no problem. The longer I waited after shutting off the longer it would take to catch. If a half hour or more, I would have to bleed again. I tried everything I thought, Finally I took the bed of the truck off and opened the fuel tank. There is a canister type thing that is attached to the cover of the tank that has the fuel gauge sender and the pickup in it. It seems there is a little resevoir that allows the driver to make it up a STEEP hill when your fuel is low and all the way to the back of the tank. It is also there with instant fuel when starting. That had broken loose from the cover and was free to do what it wanted in the tank. The return line dribbles into the forementioned resevoir and it was not doing it in this case and therefore not fuel aat the ready for starting. Weird huh? Well I brazed the canister back together and filled the tank therefore filling the resevoir and off I went, all fixed. I don't know if you have anything similar but sometimes the stuff doesn't jump out at you and it could be simple. Good luck

[JimmieD]

Yeeehaawww!

I FINALLY FOUND IT!

Checked for leaks: none. Checked return line by disconnect and run into a jug: fine. Stood there like a deer in the headlights staring at the engine. Hmmm....I wonder....?

Grabbed my jumper wire off my meter and ran straight 12V to the KSB Cold Start Timing Advance connection. Hit the key and it started almost before it cranked, just like it used to do! I still have to figure out if I have it wired wrong, which I doubt, or if the temperature sender in cylinder head is junk. Whatever, I know the source of the problem so now I can find the exact cause.

And yes, DT, it was something simple, and finding it only took about 3 months ha haha! Thanks for the help, guys!

[warlock440]

I FINALLY FOUND IT!

Checked for leaks: none. Checked return line by disconnect and run into a jug: fine. Stood there like a deer in the headlights staring at the engine. Hmmm....I wonder....?

Grabbed my jumper wire off my meter and ran straight 12V to the KSB Cold Start Timing Advance connection. Hit the key and it started almost before it cranked, just like it used to do! I still have to figure out if I have it wired wrong, which I doubt, or if the temperature sender in cylinder head is junk. Whatever, I know the source of the problem so now I can find the exact cause.

And yes, DT, it was something simple, and finding it only took about 3 months ha haha! Thanks for the help, guys!

If that turns out to not be the problem check the O-ring that is on the top side of the plate that seperates the filter from the heater..I had a 94 that when I changed the filter it loosened the plate that seperates the filter from the heater.. When I put the new filter on and tightened it up it nicked the O-ring.. It would leak air into the system but not leak fuel so it would be hard to start the first time after sitting a couple hours..

[JimmieD]

Thanks for the tip, Warlock. Yea, celebrated too soon: that wasn't the exact problem. It seems that the fuel valve which is on same circuit as KSB cold start advance mechanism is failing to open. This is the same as early 1st Gen with wax-motor KSB on Bosch VE Rotary pump. Thought it was incorrect wiring but that didn't fix it. Then thought it was the Cummins paint all over the terminal, but no.

Have now found that jumpering the fuel shutoff valve solenoid with 12V gives erratic results. Works one time, doesn't work 4 or 5 times, works again. So it may be the solenoid is weak, or the fuel valve plunger has a problem. I'll tear it apart tomorrow and see. I may install a manual pull cable to override the solenoid if the plunger is okay, just like the good old days.

Frustrating, 'cause I thought I had it, and cheap, too ha haha! Nope.

[Charles Talbert]

The shut down solenoids on the later in-line pumps go for around $400, lots of manually operated cables have replaced them.

[JimmieD]

Ha ha, you said a mouthful there! Yipes, $400... Supposedly the early solenoid valve shutoff [028-130-135-B] is available for $36 plus shipping from Valley Wagon in Carson City, NV, 1-775-882-2350. May find out real soon.

[DThibault]

You can tell if the solenoid is bad by just unscrewing it and taking out the little plunger in there, don't lose the o ring that seals it on the bottom when you screw it back in. It is the same solenoid that they use on a diesel Rabbit in the late 70s. I can get the Bosch part number tomorrow if yoiu need it.

[JimmieD]

Thank you, D/T! I'll holler at you if I end up needing the P/N but thought it might be the one I posted that's in the 1st Gen sticky.

I couldn't get to fuel valve today but maybe tonite, otherwise it's at the top of the list for tomorrow. Today was spent converting the truck's leaking '67 Mopar Model 77 heater to take a '78 Dodge truck core. Took some whittling and such but by golly, it worked! Thanks.

JimmieD

[MoparNorm]

Jim,
Tell Charles what it's doing now, I want to hear this answer! ha!ha!
MN

[JimmieD]

You're on!

Tore apart fuel solenoid valve and found the plunger was sticking. O-ring was 1/2 way up plunger shaft. Made it right with o-ring pulled off plunger and sealing solenoid body to pump housing instead. Bled it all down with manual lift pump lever. Got in and cranked it over about 6-7 revs, then tried it again: NOTHING! Huh?

Ignition switch was still on so I hit the permanent remote start button under hood: instant start, every time. Will not start any other way. Cracking the fuel line entering injection pump was not what caused it to start. It was the action of hitting remote start button that makes it start.

[Tom Petroff]

Jimmie,
So did you ever get this corrected? Sounds like to me your loosing your power to the shut off solenoid When you crank from the key.

Curious what you found.
TGP

[MoparNorm]

JimmieD can post about it in great detail, but just for the abridged version (he's real busy at the yogurt thread), it was a wiring/switch issue. All is well now....
MN