hard starting, still trying to figure out

[GREASE FIRE]

my truck has always taken a lot of cranking to start since i bought it, and it was the same when it was running only on diesel for the first few weeks as it is now with a two tank wvo system, heat exchanger, etc. It starts easily when warmed up but if it is not hot then it takes 5 -10 seconds on a warm day and even longer on a cold day.
it has a manual glow plug system and i hold the button down for about 8 seconds, and i know they are all working.

so today i tried a test - first, without the glow plugs, i cranked it for about 5-6 seconds. It showed no signs of starting, not a cylinder fired, and eventually the truck started shaking while cranking. It reminded me of a time i ran out of fuel and was not aware of what caused it to stall (leak in fuel tank and no sending unit - i thought it was almost full).
Then i gave it 8 seconds of glow plugs and it fired immediately, just like if it was hot.
usually when it starts, after a lot of cranking one cylinder will hit, then another and so on until if finally starts (and i keep the pedal floored while cranking).

So any idea what it could be? my guess is fuel backflowing while it is sitting, but i don't understand how because i think these lift pumps have a check valve built in - don't they?

thanks,
Paul

 

[G. Mann]

Go buy yourself a cheap electric fuel pump and plumb it into the fuel line that feeds the mechanical pump. Wire it to a "momentary on/off" switch and before you try to fire the engine / glow plugs, prime the fuel system with the electric pump.

My bet is that you will start instantly every time. It's also my bet that you have a leak in the return fuel lines or caps and it's bleeding off the fuel prime at the injectors.

 

[GREASE FIRE]

My bet is that you will start instantly every time. It's also my bet that you have a leak in the return fuel lines or caps and it's bleeding off the fuel prime at the injectors.

thanks for the reply.
i probably will try the electric thing as a last resort though, because my fuel system is modified a lot and there is not much room to add stuff in the line - plus the elec pump won't handle the wvo i have in the rear tank so i would have to plumb a check valve in parallel to it to ensure fuel would flow through it.

i am more interested in fixing the leak. The previous owner had just replaced the return lines with braided ones and so far i have not seen any evidence of fuel leaks there. Any idea how to figure that one out?
i may start by blocking the fuel filter return line and see what that does. When i press in the tire valve on the filter head it is obvious that there is not pressure in there because fuel just barely drips out and it should give at least one good squirt (when shut down) - at least i think. Right?

thanks,
Paul

 

[G. Mann]

It's likely that what you have is an AIR leak not a FUEL leak, so it may not show up as a wet spot.

The air leak will cause you to bleed off the fuel that should be standing in the lines to the injectors. Since the injector lines are empty, the truck will crank and crank while the engine pump refills the filter and lines, thus hard starting when cold. Once you start and run the lines are full and it restarts easily.
Classic symptoms of an air leak.

Try the electric pump trick. I bet you like it.

 

[dbarilow]

How many miles on the IP?

 

[GREASE FIRE]

i don't think it is the pump - i have some experience with these things from my 6.2 and i know how they behave when worn out.

the one thing i still don't understand about the air leak thing is, how would the injectors lose prime if the return lines were leaking? i thought they only popped open at a certain pressure - so how could fuel be leaking when shut down; and how could there be an air leak in a pressure application with no fuel leak? My experience with air leaks is that they happen on suction applications, where as in pressure applications it becomes a fuel leak.

does this make sense or not? maybe these injector return lines work different than on a 6.2?

thanks,
paul

 

[Papabear]

get beru glow plugs they are the hottest on the market and they are garunteed no to mushroom from over use

 

[ull7]

X! THE MECH! AIR IN FUEL IS THE ENEMY!!!!

just went through dealing with the lift pump going and here is what I learned! on a 85 non turbo 6.9 greaser
adding a electric pump before a bad lift pump will work for a little bit but it will go eventually at the worst time! You will be much better off with getting rid of the Ford air leaking water seperator and installing a sedimator after your heat transfer unit, clear glass bowl type so you can see when it needs to be cleaned, fuel when it is hot will seperate from water much quicker. also after you bypass the lines on the mech make sure to plumb the inlet and outlet together so even though the mech has gone bad it still is doing a cycle and not puffing air out the front of the pump. and also learned on the 6.9 you run the risk of if the mech is bad it filling your crankcase fill of fuel!
I did the electric conversion not even a fancy pump 40 bucks from auto z and it starts better than ever and burns the wvo much better! also make sure that all of your glow plugs are working it only takes two bad to make it a
pain to start! air is the enemy!!!! further note all this was learned the hard way!!! Filter first before you drop it in the tank!! dont turn the enginebay in to a filter sub system!!! Heat exchanger,Sedimator,stock fuel filter. keep it simple! much easier to change one filter than two or three!Ford Water seperator? What the f where they thinking when the put that piece of @#@# on a great engine! get rid of it!!mech fuel pump yea sure if you want to put a starter or two in!! crank!!! pls baby crANK COME ON!! cRANK ***!!START YOU DAM THING!! ! ..ELECTRIC FUEL PUMP FLICK SWITCH ON, TAP PEDAL GLOW CYCLE VROOM RIGHT UP!!!!!

 

[BigRigTech]

Is your lift pump wet? Mine is wet from using WMO and I plan to replace it before winter....Air is air regardless of how it gets in...It sure sounds like a bleed down issue to me....Maybe try a check valve in the return line to the tank and another after the lift pump...If she lights right off and then develops a rough spell it will show you which side of the system the air is getting in. Will it start better if you hold the pedal down about 1/4 while cranking?

 

[david85]

Something to check to see if air intrusion is the problem is to remove the fuel filter (assuming you still have the stock filter) and see where the fuel level is inside. It should be full right to the top and may even spill a little. A dead giveaway for air leaks is when the fuel level in the filter is only 3/4 full.

How did you verify the glow plugs are working?

They need to be unplugged from the wiring harness before doing a continuity test.

 

[cash]

I read somewhere to put a clear rubber hose in place of the return that comes off the filter to #1 check that after sitting over night. then watch as crank it over. look for air.
sounds to me like that should work. Mine checked out clear but I still have starting problems

 

[1989f2507.3idi]

were should i mount the electric one in the engine bay or frame rail?i got an air leak and maybe a bad ip

 

[david85]

were should i mount the electric one in the engine bay or frame rail?i got an air leak and maybe a bad ip

As close to the tank as possible. So, in the frame rail. Its recommended to bypass the stock fuel pump if you add an electric pump.

Although fixing the air leak would probably be cheaper.

 

[Diesel JD]

In my opinion the air leak needs to be fixed, electric pump or not. That being said, if everything is dry its not going to be real easy to find out where your air is coming in. Check all your hard connections, fittings etc. What year is your truck is it a 6.9 with the factory separate water separator? If so, that may well be the problem.

 

[1989f2507.3idi]

7.3 89