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rebuilt built 6.5l Hard Hot Start

cub124

cub124

Half Moon Detroit #1
Messages
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Location
stormstown PA
Hey guys, it's been awhile since I've posted anything but before I swap the injection pump out I thought I would get some input.
Just finished a 6.5l build for my '82. Specs as follows: 1994 block with mechanical IP, bored 0.020 over, Delta Hot cam (I think the hot one is the 206), square pre cups, 3,800 psi injectors, old Walbro electric lift pump and 0.010 over head gaskets. The injection pump is a military pump converted to 12v and the fuel screw is maxed out.

The issue is it will start okay when cold but once the engine is warm it doesn't wanna start until you crank it for awhile. I have tried to pour water over the head of the IP with little luck (its also hard to get to with the water to air intercooler there). I also tried advancing the timing some which didn't seem to help any.

I still need to plumb in the lift pump pressure gauge.

Does anyone have any thoughts other then lowing the pop pressure on the injectors because there's no way you'll talk me into that! :)
 
Take off 1 injector line and let it spray into a jar for 30 seconds while running cold. Get the truck hot so it has the problem. Then remove the same line and do it again. Measure the volume and check for differences. That will confirm or shoot down the big fear here.

Yeah, sounds like you already know that higher pop pressure is going to work that pump a touch more and have it harder to get to those numbers with a worn ip head. Maybe run the injectors for spray pattern, if they are starting to go down hill it will effect it a bit at that pressure.

Fingers crossed...
 
I'll have to give this a try.
I've also heard of mixing 1/2 gal of oil with a few gallons of diesel to see if the higher viscosity helps hot starts. If it does help, the pump head is worn.
The volume measurement is more of a hard data result though.

I was hoping to hear injection pump timing could be the issue but I don't think I'll be that lucky plus it seems to run good once its started. Also I just got the lift pump pressure gauge hooked up. The pump builds about 6 psi before cranking. (it is rated at 10 psi)
 
Need to know input pressure when it starts good vs bad to see if there is any difference.

Problem with oil in fuel as diagnosis is your lowering the flash point which in itself makes it a little harder to start. Adding oil to get more life out of the pump before know it wears out, and it will help once worn out last a tiny bit longer. Really the cold water for hard start is the best fix for a temporary deal until you can tear it down. A funnel can help get it where your u need the water.
 
Hot RPM cranking? 150 RPM or forget it! Starters can crank slower with heat as well as connections, batteries, etc.

Glow plugs?

As in are they self limiting and are you overriding them to start hot? This also helps a worn IP start.
 
Well after messing around with it I'm about 99% sure its the IP. It does help slightly to pour ice water over the head. Thanks for the funnel idea, I should've thought of that myself :banghead:.
If the rebuilt engine stays together at the truck pulls coming up I'll swap the IP out with a spare I have after the pulls. (knock on wood)
 
Finally got the reman 4911 pump on from Pensacola diesel. They were able to get 100 cc's from it at 1000 rpms (They didn't state the pressure) They did however say the pump has a new head & rotor from Stanadyne.
However I still seem to have the same hot start issue as before. If not a bit worse.
WarWagon,
I know you have messed around with pop pressures before. Have you ever had them up around 3800 psi? I'm thinking this might be the problem, or maybe the timing is way out of wack due to the mix of high pop pressures & a maxed fuel screw although I would think the combo of those two would about cancel each other out.
 
Did you mix in a lot of oil with your fuel like you talked about before? If so make sure you're starting with fresh diesel.

I Believe AK is correct, higher pop pressure injectors retards the timing, and so does maxing out of fuel screw slightly retard the timing.

Have you done a compression test?

Did you install a clear 1/4" fuel return line coming out of the injection pump to watch for air intrusion?
 
How is the diesel clatter at idle, 45 MPH low throttle, and then how does it change when you add fuel at 45MPH? If it quiets down as heat is added to the prechambers at 45MPH your timing is dead on. Lack of tools and specs has us timing most of these by ear. I did get it set once by a shop and it was a waste of money.

Check glow plugs now and then for erosion indicating too much advance.

I have higher pop pressure, I forget what at the moment, and had to advance the pump to clear up white smoke at idle. IMO the pump is wonky with too much timing just off idle so YMMV.
 
Thanks for all the input!
I have a lot of clear fuel line on it but not coming off of the pump. I should put a piece on there. There is still air coming through the injector returns but I've never had a fuel pump issue this stubborn. Normally after a short drive the system is primed fairly well.
I have not pulled a compression test but it wouldn't hurt.
The current fuel mix is 11 gallons of Diesel, 1/2 quart of engine oil, 1 quart of cooking oil, and some Diesel Kleen + Cetane Boost.
I did try advancing the pump more without any luck so far. I'll try advancing it even more when I get a chance.
It seems to be cranking fast enough (by ear)

WarWagon, I know what you mean, that's how the last pump was timed - It worked great there.

I agree the higher pop pressure retards the timing but I thought maxing out the fuel screw advanced the timing some due to the peak pressure being obtained faster?
Should I be concerned about the quality of the reman pump? Thinking back the head & rotor might be a reman from Stanadyne not a new one.
 
Kinds missed it eariler, but, you need to drop "Pensacola diesel" into Google. Read the 1 star reviews or the words "Stay Away" come up often...

I see another IP swap and "fun refund" process in your future. :hungover:
 
Well it looks like I need to do a little more homework before I buy next time. I called them and they said I could return it so I sent it back and a few days after they got it I called them again to see when they were going to issue a refund. Well it turns out they already put a different head and rotor on it and sent it back to me. So I gave them the benefit of the doubt
and decided to give it a try. The head and rotor is definitely better. Is it a reman? I doubt it, it looks used without much of a reman touch.
After getting this pump bled out enough to run I've put about an hour of run time on it.After they had it the idle seemed to be set way to low and a couple of other problems have arose.

1) After revving the engine it will stutter and sometimes shut off. (depending how high the idle is set)
2) Air immediately makes its way into the IP return line after shutting the engine down. Is this normal for the IP return line?
I've had clear lines on the injector returns for as long as I can remember and I never saw this happen. However when the engine is running the IP return line is filled with fuel.
3) The engine won't start without glow plugs after sitting when its still warm (say 150*). But right after shutting it off when warm it will start back up. (my theory was the head & rotor gets a heat sync which after using ice water it didn't seem to help, only after I cycled the GP's did it fire) :banghead:

Thanks in advance for your 0.02¢!
 
Last edited:
Sounds like something is going on with the advance piston.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 
Are there any external adjustments that can be made such as clocking the tapered advance arm that is clamped to the throttle shaft?
Or do you think its an internal problem from scouring in the cylinder wall causing the piston to hang up during a quick snap back of the throttle?
 
Internal.
I don't know about over here, but for the Ford idi guys, they like to try the "atf trick."

Sent from my SAMSUNG-SM-G890A using Tapatalk
 
79jasper said:
Internal.
I don't know about over here, but for the Ford idi guys, they like to try the "atf trick."

Sent from my SAMSUNG-SM-G890A using Tapatalk
Click to expand...

On a rebuilt IP there should be no tricks. It either works or send it back. Call credit card company and start a dispute. However you have to eliminate air first... Air is the #1 thing to test for and fix even in the GM manual.

To the OP:
Air coming out of the IP return line is a problem and would be the cause of your problems. Injector return lines having air is not a clear answer far as I know and I don't bother with those.

Running an hour should clear the air up in the IP return line. Because you are still seeing it it IS a problem. Air is generic for "not liquid diesel". If you have a kinked hose, plugged fuel filter, plugged tank sock, bad or clogged lift pump, pinhole in the fuel lines or pickup assy in the tank... Anyway a restriction will put a vacuum on the fuel system from the rotary pump in the IP. This vacuum will boil diesel in the fuel line literally vapor locking the engine.

Are you still running the mechanical lift pump on the engine? Do you have a pressure/vacuum gauge and a place to tap it in like the water drain on the fuel filter?

Check for kinked hoses and kinked or leaking steel lines. Any fuel leak is an air leak while running and some air leaks don't leak fuel.

You need to put clear lines from the lift pump and before it to pin down where the air is coming from. Even put a clear line before the IP just in case the internal screen in the IP is plugged.

The IP returns a lot of fuel and is RPM dependent - higher RPM, even with no load, returns a lot of fuel to the tank. So idle may be fine but high RPM may show a restriction or bad lift pump. Even the lift pump cam lobe can wear down and cause a high RPM dependent fuel starvation problem.
 
pensacrap yes it is.
Warwagon, I agree there should be no tricks I was just hopeful I might be able to get it to work.
The truck has an electric lift pump, I think its the FRB-5, with a pressure gauge, it holds 4-6 psi fairly well. New fuel filters and the engine ran fine with another pump I had that has a known bad head & rotor. There is clear line leading to and from pump and all is well with the supply side. The return line has been checked with an air compressor and the lines are clear.

I agree normally after an hour there's no hiccups at all.
So I got frustrated and called them and told them I thought it was an internal timing issue and they said "well send it back we'll look at it, fix it and send it back to you", I told them it's being returned for a full refund this time because it didn't work the first two times I'm not trying #3. The lady didn't argue with me so hopefully it will work out. Needless to say I'm not putting that pump back on even if it does show up in the mail again.

Now time to shop for a real pump builder!
 
Have you talked to the vendors here? Idk about Leroydiesel.com if he is sells an IP or not. But unique diesel.com sells built up IP. Calling them guys and find out what they can or can't do for you would be my starting point.
 
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