Losing prime

[NIsaacs]

It's a brand new Bosch VE.

Genuine or aftermarket? I bought a new aftermarket for my '91 and it was bad out of the box. The second one appears to be fine.

Years ago I worked on a 90 model D350 with the same symptoms you are having. No cold start, white smoke when you used starting fluid to start it. A rebuilt pump fixed it.

My bad new pump....

 

[Mark P]

Which KSB do you have, Wax or Solenoid?

I really don't know them apart, but with a non I/C motor, I thought it had to have power key on. I parked the truck on a very steep incline last night, and this morning, it was even harder to start. Once I got it running, and idling good, I unplugged the KSB, and it started to chug to the point that the whole truck shook. Once I plugged it back in, it ran great again. I just looked online at the 2 different KSBs, and mine is the one with what looks like a shut off solenoid on the end toward the cab of the truck. The solenoid looks just like the shut off solenoid to shut the fuel off to the pump. The other KSB appears to have a long solenoid on the end.

 

[Mark P]

Genuine or aftermarket? I bought a new aftermarket for my '91 and it was bad out of the box. The second one appears to be fine.

Years ago I worked on a 90 model D350 with the same symptoms you are having. No cold start, white smoke when you used starting fluid to start it. A rebuilt pump fixed it.

My bad new pump....

It has all the Bosch tags on it, so I'm assuming it is a genuine Bosch. It has no leaks that I've seen so far..

 

[Mark P]

It has all the Bosch tags on it, so I'm assuming it is a genuine Bosch. It has no leaks that I've seen so far..

This is the pump. You can see the Bosch tag.

 

[Ozymandias]

That's the solenoid type you have, so it's all good with the power to it.

 

[Mark P]

So..... parking it nose down didn't do anything for it. Is it losing prime????? I thought about unhooking the line above the T and putting a rubber hose on it, and putting the other end in a bucket of diesel.

Now, if it were a timing issue...like too much advance, then unplugging the KSB should help it, but it made it worse. It runs best with the KSB plugged in with key on power. As for the timing, I set it up on the "C" on the gear, instead of the "E", so it should have more advance than factory (10 degrees more). Being that the pump is a new Bosch, and not a reman or a generic, it should be good to go. This thing runs fantastic, once I get it started. I'm very pleased with the performance. I set the valves at .010" I and .020" E, so that should be fine. I've seen different specs on the exhaust valve lash. Some spec it at .026". Not sure if that would make enough difference or not. I don't see any leaks between the pump and the injectors. To bleed off there, it would have to leak fuel. As soon as I turn the key and run the FASS, it has 11 psi fuel, so I don't see the pump bleeding off. Any ideas from there???? I do appreciate all the ideas and input!!

 

[BigPapa]

I don't know enough about the VE to help. Maybe post up in the 1st Gen Forum and maybe one of those fellows will see it and jump in.

 

[petersonj]

A puzzler. What is puzzling is that you say the engine runs very well driving the truck after warmup, but yet is difficult to start.

You mentioned earlier that you had about 4 inches of fuel in the tank and that you were going to fill the tank. Did you do so? If you did fill the tank and parked the truck nose downhill, then I don't think you are having a loss of prime problem. If you didn't fill the tank, the test may not be valid.

Now, if it were a timing issue...like too much advance, then unplugging the KSB should help it, but it made it worse. It runs best with the KSB plugged in with key on power.

I tend to agree with that. Years ago I ran truck with a 4BTA engine in it. It used a VE pump. EPA required the wax crystal advanced timing unit for cold engine operation. I experimented with disconnecting the unit and the engine was much harder to start in 20 degree weather than it was with the unit connected. So, the advanced timing was beneficial in cold weather.

Is there a possibility that there is a fuel quality problem? Contaminated fuel? Just brainstorming.

- John

 

[Mark P]

I don't know enough about the VE to help. Maybe post up in the 1st Gen Forum and maybe one of those fellows will see it and jump in.

Good idea!! Thanks!!

 

[Mark P]

A puzzler. What is puzzling is that you say the engine runs very well driving the truck after warmup, but yet is difficult to start.

You mentioned earlier that you had about 4 inches of fuel in the tank and that you were going to fill the tank. Did you do so? If you did fill the tank and parked the truck nose downhill, then I don't think you are having a loss of prime problem. If you didn't fill the tank, the test may not be valid.



I tend to agree with that. Years ago I ran truck with a 4BTA engine in it. It used a VE pump. EPA required the wax crystal advanced timing unit for cold engine operation. I experimented with disconnecting the unit and the engine was much harder to start in 20 degree weather than it was with the unit connected. So, the advanced timing was beneficial in cold weather.

Is there a possibility that there is a fuel quality problem? Contaminated fuel? Just brainstorming.

- John

I didn't fill the truck, but it has over 3/4 of a tank now. With the pick-up just forward of center on the tank, pointing it downhill would more than cover it all. I've considered running independent return lines from the head and from the injector pump to see if it makes a difference.

As for fuel quality, I have run "black diesel" for the past 80,000 miles or so. It's a mixture of diesel and used motor oil, and I filter it to 3 micron. I run it through a 2 filter set up, with the first filter being 16 micron, and the 2nd one is a 3 micron with a water separator. Factory Cummins filter is 4 micron. I don't think that could be it, since I've ran it in this truck just prior to the teardown and VE install. After adjusting the star wheel in the AFC, and turning the fuel screw in, I was really impressed with how it runs. I can't see it being a problem with the pump. I put new filters on the FASS also. I use Wix filters. I've even checked the voltage to the fuel shutoff solenoid.

I'm running out of ideas, but I'm not one to give up.

 

[Matt42]

I didn't fill the truck, but it has over 3/4 of a tank now. With the pick-up just forward of center on the tank, pointing it downhill would more than cover it all. I've considered running independent return lines from the head and from the injector pump to see if it makes a difference.

As for fuel quality, I have run "black diesel" for the past 80,000 miles or so. It's a mixture of diesel and used motor oil, and I filter it to 3 micron. I run it through a 2 filter set up, with the first filter being 16 micron, and the 2nd one is a 3 micron with a water separator. Factory Cummins filter is 4 micron. I don't think that could be it, since I've ran it in this truck just prior to the teardown and VE install. After adjusting the star wheel in the AFC, and turning the fuel screw in, I was really impressed with how it runs. I can't see it being a problem with the pump. I put new filters on the FASS also. I use Wix filters. I've even checked the voltage to the fuel shutoff solenoid.

I'm running out of ideas, but I'm not one to give up.

I'm watching this thread with considerable interest. My truck runs a P pump, so there isn't direct applicability. But the sleuthing is really interesting.

My first thought was a pinhole leak in the fuel return line was causing loss of prime. But it looks like that is not the issue.

 

[Mark P]

Just a FYI........................ After I drove the truck yesterday, I turned the fuel up a little more, and turned the start wheel 1 3/4 turn down in the AFC to bring the fuel in sooner. Today, it has seemed to start worse than ever before. I've used it on the farm some today, and every time I've started it, it coughed white smoke, and took about 5-10 seconds for the engine to clear out. It sounds like a gas engine that is flooded. I just turned it all back to where it was. I try to track every move, just for this reason. That brings me back to the pop pressure on the injectors. Runs great, but starts hard. I don't remember the specs on the VE vs VP44, but I need to look into it. We have a local diesel shop that builds pumps and services injectors. I may give them a call tomorrow.

 

[Topzide]

@Mark P, Like the fact that you're keeping track of the changes. Maybe keep a notebook in the truck to write it down. You'd be surprised when you do this, then study it, you may find the answer through the trends that you were doing. I think you're hunting down the right trail by contacting the shop to inquire in the pump differences and pop off pressures needed. Good luck!

 

[BigPapa]

I don't know about the pump pressures, but I posted the injector pop pressures earlier.

The 1st Gens pop at 3550psi, the 24-Valve injectors pop at 31,026kPa (4500psi).

 

[Ozymandias]

Did you use new Cooper rings at the install?

 

[Mark P]

Cooper rings?? Not sure what that is or where they go.

 

[BigPapa]

I think he meant "copper"?

 

[petersonj]

I just went through and reread all of the posts. I didn't see any mention of putting in different injectors - injectors that would be compatible with the VE pump. As @BigPapa mentions - a big difference in pop-off pressure between VP44 injectors and VE injectors. Since the VE pump is not designed for those high pressures, maybe the injection pump is having difficulty reaching those higher pop-off pressures during engine cranking. It kind of makes sense and does coincide with the symptoms you are having.

- John

 

[Ozymandias]

I think he meant "copper"?

Yes

 

[Ozymandias]

I just went through and reread all of the posts. I didn't see any mention of putting in different injectors - injectors that would be compatible with the VE pump. As @BigPapa mentions - a big difference in pop-off pressure between VP44 injectors and VE injectors. Since the VE pump is not designed for those high pressures, maybe the injection pump is having difficulty reaching those higher pop-off pressures during engine cranking. It kind of makes sense and does coincide with the symptoms you are having.

- John

Excellent, good point that you have seen this.