I began having problems starting my '86 6.9 over a year ago. It started out with diffuculty starting the truck after sitting overnight. Nothing bad at first...maybe 3 tries before it would fire. This gradually worsened to the point where I decided to replace the return lines...this made no difference. Then last fall things reached a point where the fuel system had to be reprimed everytime I started the truck...even if I shut if off for 5 minutes to run into Lowes. Then in November the problem reached the point where it would occasionally shut off while I was driving...usually when making a slow turn. At that point I was ready to let it sit for the winter anyway so I've done nothing with it since then. This past weekend I decided to have a look. Well, I couldn't even get the truck to fire. I did check the fuel flow at the filter and that appears to be fine...I had a nice pee stream when I cranked the engine over. I then checked the fuel flow at the outlet of the IP and it was a trickle...this appears to be my problem.

Before I spend the coin to buy a new IP I wanted to hear from some members if the IP is definitely the problem or if there are some other things I should check first. I've read quite a few posts in the archives where members replaced the IP but their starting problem remained so any and all input would be appreciated.

Thanks.

Tim

 

The water separator on that year I believe is a big air leak problem. My truck did not have one and I got one from this site and refurbished it- no problems. Also, I think that there is an internal screen at the IP fuel inlet -ask around, there seems to be some snafu about accessing it. I don't know if this is similar, but I have a JETTA with an accessible fuel cut solenoid- It needs to be replaced, but every once in a while I need to remove it and check the seat otherwise fuel returns to the tank and I have a hard start if I let it sit. I hope this helps.

 

I second the water seperator.
Put a bolt in the drain line after you drain it.

The problem was the drain does not seal ofter you drain it, so since it is on the suction side of the lift pump it sucks in air.

 

Dave - it's about time I heard from you. I put a bolt in the water separator last fall when I was trying to figure out the problem (and it's still there) but I didn't drain it first. Should that make a difference?

 

Not unless the seperator is full of water.

You may want to inspect the steel fuel lines between the tank selector, water seperator, lift pump and fuel filter.

Look at the line from the lift pump to the fuel filter.
The heater (raised place) on mine had corroded the line to the point it was leaking fuel.
When the engine was not running, it let air into the line.

That one took me a while to find since it acted like a return line problem.

 

i had almost identical problems thought it was the water separator ,fuel filter light would not shut off , ne how it turned out to be the fuel pump 33 dollars at Napa and 45 minutes to install I regained lost power no warning light was on either ,one minor problem is that what stopped the fuel pump was the push rod falling off into the oil pan which is my latest dilemma on ehat to do about the missing push rod

 

No push rod in the IDI motor, the fuel pump arm rides against a cam.

Or did the arm break off?

 

yeah thats what i meant unfortunately the arm wasnt attatched to the pump when I removed it

 

Here is the latest...I pulled the lever on the water separator and I didn't get a drop out (I 've had a bolt in the drain line since November). I pulled the inlet line off the fuel (lift) pump and a trickle of fuel came out. Shouldn't I have had a decent amount...I'm thinking at least the distance between the water separator and the fuel pump?

 

My system will siphon back to the tank when I drain it, so I have to clamp the supply line to the separator. The supply to the mechanical pump (my truck) should drain some fuel. When I refurbished mine, I noticed a material in it that could possibly plug up.- I don't know. But if you loosen the metal line at the pump to the filter there should be that line that will drain.

 

I just had one in the shop today with the same problem now thats kinda funny.

The last time it ran did it blow white smoke like it was sucking air? I did all the usual checks and it also had 6 month old return line kit threw a remaned pump on it and Whoop Bang problem solved.

Also before that pull off the top of the pump check for junk pull out the return line check valve do-hicky also do an over all check of the inside of the pump.

The one I did today had all kinds of metal shaveings in it.

 

You guy's are working on the same problem I have. Sofar I have done the following, without improvement, and with all the cranking burnt a starter out.
Changed the lift pump and HP pump from my 84, replaced the o-rings on the injectors, checked all lines and connections I could see. Still the same.
This 87 engine does not have a water separator on the OEM filter, I have a separate Racor pre-filter with water separator. The OEM fuel filter is full after a night's parking. The starting problem is not only when engine is cold. After running the truck, 30 minutes later I already have starting problems. Could it be the injectors? I have a set from the 84 engine. Should I install them? Once the truck runs, it runs fine. Any ideas???

 

These IP's that we have, they are an axial rotary type, right? If so, don't these units have one plunger and 8 check valves- one before each line? Can't these valves affect injector opening (timing) and can leak back to the pump preventing a full function/ or operation of the injector. Just a thought.

 

I have changed the HP pump already with one that gave no problems on the 84 engine. Still the same problem. This is a boner! I have 3 other diesel vehicles, a Mercedes 300SD 85, Duramax 2002 and a Volvo Penta 200 HP 95 diesel in the boat. Never had this type of a problem. Some merits in changing the injectors?

 

Based on what I've read it sounds like my next move should be to bypass the water separator and see if that solves the problem. What kind of fittings will I find on the water separator?