multifuel injection pump overflow valve

[will-m]

My deuce has always been been a slow starter and I've decided that I wanna try to take care of it. I've always suspected that it was fuel leak back, because other then starting the truck runs great, has good power, no excessive smoke or oil consumption. I've checked the batteries which were showing 26volts, all the fuel filters are new, straight fresh diesel. I've also checked the intank pump and confirmed that it is pumping fuel. I've checked all the fittings for the injectors and flame heater return lines and can't find any leaks. The fuel shutoff is all the way in, and I've removed the cover to ensure that it cycles smoothly. Today I noticed some bubbles in the clear fuel line coming up out of the overflow valve on the injection pump after shutdown. From some other threads on this topic I'm thinking this may be the problem. I looked in TM 9-2910-226-34 but didn't see anything about how to check the valve. Any help would be great. thanks

 

[m-35tom]

does it hold pressure? does it have 20 psi or more when cranking?? measured at the bleeder on filters

 

[will-m]

I haven't checked that yet. I'll have to go pickup a pressure gauge. thanks

 

[m-35tom]

get a 0 to 100 gauge that has a big enough scale to show 5 psi.
actually i don't think any of them will hold pressure since there is a bleed feature in the overflow valve. put the gauge in the bleed port of the filter assy. it should read 5 psi with just the pump on engine not running. cranking must be 20 psi, 700 rpm must be 30 psi and after it is warmed up run it at full throttle and it should be 60 to 80 psi. this will eliminate any fuel supply problems if all readings are as given. next would be timing, very easy to check, ip head weak, injectors dirty (my guess, have yet to see a truck with 6 good spray patterns) slow cranking? should be 300 rpm

 

[will-m]

Just checked it out with a pressure gauge and the results were:

5 PSI with motor off with electric pump running

40 PSI at about 800 RPMs

75 PSI at full throttle

While cranking I'm only showing about 5 PSI and it drops off as soon as the motor is shut down. Back to 5 and then to 0 when the ascessory switch is turned off.

What would you suggest? Thanks again

Cranking is right around 300 RPM

 

[cranetruck]

Numbers look good, even the cranking speed is very good.....

 

[ken]

Try giving it 1/4 throttle while cranking. It it starts quickly. Then increase the fuel rate slightly. You can barly hear the starter on mine even if it's been sitting for weeks.

 

[will-m]

I normally start it with the accelarator slightly depressed until it starts to fire and then let off so it can build oil pressure. Even when doing this it still needs to crank for 10 seconds or more before it fires. After the truck has been started and warms up it will restart quickly for the rest of the day. Anybody know what would cause the low fuel pressure while cranking? The truck does run rough for a few seconds when if first starts, but smooths out as soon as the fuel pressure starts to climb. Seems like the low cranking pressure may be the culprit.

thanks for all the suggestions

 

[jwaller]

I'd bump up the delivery rate. what is your egt's on it at wot?

 

[m-35tom]

it sounds like the overflow valve is not seating at low pressure. i would swap it with another and see what the cranking pressure does. it is important to have enough pressure to charge the ip head plunger.

 

[will-m]

As far as the EGT's I'm not sure as I've yet to install a pyro. Ordered a overflow valve from Memphis and it should be here tuesday. I'll report back after I swap them out.

Thanks

 

[will-m]

Changed out the overflow valve last night. The truck does start much faster when warmed up. Went out tonight to see how it did when cold and it does start faster but still requires some throttle to get the motor to catch. The fuel pressure at 800 rpm's went up from 40 PSI to about 45 PSI, but I'm only getting about 10 PSI while cranking (up from 5 PSI before). Any suggestions on what to check next? After looking a little closer I also noticed that I'm probably only cranking at about 225-250 rpms.

Another question, I got the truck to fire without bleeding the fuel system. Is it still necessary to bleed it. I assumed that running would force all the air out. Just want to make sure. thanks

 

[m-35tom]

you could just have a worn ip head plus timing is critical, check it. take the little piece on top and in front of the ip head off, 4 small bolts. turn engine until pointer lines up with line, look at timing marks on front pulley. do all this with the shutoff pulled out so it won't start.

 

[will-m]

Alright I'll give that a try tonight or tomorrow afternoon and report back with my findings. thanks

 

[will-m]

Ok just took a look at it. It looks to me like the timing might be slightly off. Its hard to tell because I can't really get a straight on look at it. I'll try to get a real pic of it tomorrow. I made up a little drawing in paint of what it looks like. The pointer doesn't look centered on the timing mark on the pulley. It's off by maybe 1/16" or slightly more. The motor is a LDT-465-1D with a C turbo.

 

[will-m]

Ok here's the pics, hope they work. I'm not sure if its just the angle but it looks a little off to me. I'm not really sure how close is close enough though.

thanks

 

[cranetruck]

Changed out the overflow valve last night.....

Did you inspect the original overflow valve, how does it look?
Just curious.

As far as bleeding the fuel system, do it before starting the engine each time and find out if you routinely get an air pocket at the secondary and final fuel filters.

Starter cranking speed of 200 rpm is nominal at about 70°F.

The timing should be okay from the looks of it, IMHO.

 

[gringeltaube]

Try to advance it just a little bit.

 

[will-m]

The original overflow valve looked ok to me. I took it apart and everything seemed clean inside. No signs of anything that would cause it to stick. I'll take a look at advancing the timing.

Thanks for the replies.

 

[will-m]

Does anyone else think that advancing the timing might help? I looked in the TM and it looks like a big project. Can it even be done without pulling the radiator? I'm going to check the pump timing tomorrow if I can get a break in the rain. Any other suggestions? I'll also start it a few times and see if I'm getting air in the system.

Thanks