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 top 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....

 

Return lines OK? Not crimped or kinked?

 

Wide open, blew them out with compresed air when I installed, re-checked today and all looked good. Rubber fuel injection hose on either end, solid steel line. F/I hose is all that's available around podunkville....

 

OK, I'm stumped too. Will it keep running when you retighten the fitting?

 

Runs great! Engine note/pulse doesn't change at all when fitting is tightened after it starts. First diesel I've ever heard of that wants LESS fuel pressure to start!

 

You have the piston pump or a diaphragm pump?

 

Diaphragm.

 

Dang, you're not helping me here.

I gotta say it sounds like a problem with the injection pump. There is absolutely nothing wrong with the supply system.

 

I really can't find anything wrong with anything at all. It seems especially strange that it runs just great soon as it starts. The engine is quite noisy, even more than I expected, like the valves may need adjustment, but other than that: GREAT!

It's gettin pretty bad when you have to install a starter button under the hood.... Maybe I'll try to splice in a 12VDC solenoid actuated bleeder that dumps to the return line?

 

I FOUND IT!!!
After 3 months of going round-the-bend nuts looking for the problem I finally found it: KSB.

On an impulse I grabbed a jumper wire and juiced the KSB wire connection with straight 12V. Turned the key and it started almost before it cranked over!!! Now I just have to figure out if I have it wired wrong or if the t-stat in cylinder head took a dump. I have it wired to get 12V at ignition 'Run' position, but maybe it needs to be at 'Start' position. By the way, engine will not shut off with KSB jumpered like that. Jumper has to be removed and then switch off.

Thanks for the help these many times trying to diagnose the problem, Wanna!

JimmieD

 

ok call me a dumby. KSB?

 

Oh, that's an abbreviation for the German words 'Kalb Schnechteriegesungenden Bestetlleinkeidenze auf wedersen.' Sorry, I should have been more clear on that.

Actually it is the abbreviation for the Cold Start Timing Advance System [KSB] Temperature Switch. It's that gizmo on the driver's side of the VE pump, kinda torpedo shaped with a fuel line or two and a wire going into the firewall end of it. that wire goes up to the temperature thermostat in cylinder head, almost behind pump but slightly rearward.

 

That's weird. Is it a wax motor style KSB or an electromagnetic one? Wax motor style is cone-shaped, while the electromagnetic one just looks like a nut with a terminal.

 

Not weird, brother, sorta stupid. Remember, I'm a diesel dummy, first one I've ever even been around!

I have to go out right now to sort it out, but apparently I don't have the 12V feed to wax motor KSB and FUEL SHUTOFF VALVE wired properly. Rewired the entire truck and changed it to a circuit breaker buss-bar system and pulled power for KSB/Fuel valve off of what I thought was 'Ignition run' bundle. Well, somehow it ain't workin so I just have to re-terminate that wire. Found that truck won't shut off when KSB/Fuel is jumpered [of course] so just have to make it right.

I'll probably go to a separate circuit and hidden switch, and wire fuel valve independent, no KSB. EPA can kiss my smokey pipe on white smoke at startup

 

Humorous update, real thigh slapper. When they painted the engine they didn't have it installed in chassis. You know how Cummins is about their 'INDUSTRIAL GRADE PAINT', right? Yea, they made sure to get the paint real good and thick right there on the fuel shutoff solenoid wire terminal. Cleaned paint off so I could get some electrical continuity and whaddya know, it starts. Thanks, Cummins