85 6.9 IDI Will not run

[BMadScientist]

Good Evening. I’ve got a 1985 F350 with a 6.9 as the title suggests. I bought the truck a little while ago and up until now it’s been fine. The truck has a R&D Performance RD2-80 aftermarket injection pump. The truck had a Holley Black electric fuel pump on the frame as a lift pump which has a max output pressure of 14 psi. The pump went out a few days ago so at the recommendation of a friend I put a new body style 7.3 power stroke Bosch lift pump on so I would later have the ability to run waste oil, and replaced the fuel filter. I was not aware of the pressure output of that pump (60+ psi) and went ahead and plumbed everything in and found that the truck ran like ****. Bled the fuel lines, checked for air at the pump return port with a clear line and found no air bubbles. The truck would kinda idle ok but has no power, when pushing the pedal to full throttle, the rpms would slowly rise to around 1500(guessing, no tachometer) where it would sit for around 3 seconds before rpm’s raise all the way to what I assume is fuel cutoff at 3800 rpm. I did some research and found that it seems the stock injection pump wants around 5-12 psi of fuel at the inlet. I’ll save the details of this debacle but I put a bypass style regulator on the truck which allowed me try and regulate pressure down to between 4.5-9 psi at which point the truck basically wouldn’t run, it would only idle with at full throttle and die as soon as you let off the throttle. Cranked the pressure regulator all the way closed and blew up my pressure gauge so assume I was getting the full 60 psi of fuel pressure again and it was back to having no power and raising to 1500 rpm and then rocketing off to 3800 rpm. I’ve got another fuel pressure regulator on it now and can crank fuel pressure up between3-20 psi and if I change the spring anywhere between 3-70 psi. Frankly I’ve been at this for 3 days now and I’m throwing my hands up and pleading for help. Did I damage something inside the pump? Is there some crazy inlet pressure that I’m not aware of that’s specific to the R&D pump that I’m not aware of? Is there something I’m overlooking?

 

[Olds64]

With that PSD fuel pump putting out too much pressure you're shooting yourself in the foot before even trying to start the truck. Replace the fuel pump with at least a parts store cheapie and then see if you can get the truck to start.

Here's one that's less than $100 on Summit. You could probably get one even cheaper on Amazon.

Pardon Our Interruption

Better yet, get a Facet Duralift electric fuel pump. Here's one that's well reviewed for our IDI trucks.

Facet Dura-Lift 12v Fuel Pump, 1/8 NPT, 9-11 psi, 120" lift | Pegasus Auto Racing Supplies

The Facet 40222 Dura-Lift Fuel Pump can draw fuel from up to 10 feet away. Great replacement for the lift pump on 83-94 Ford diesel trucks and vans.

www.pegasusautoracing.com

Be wary of cheap imported imitations of the Duralift pump.

 

[BMadScientist]

I appreciate the reply Olds64 but can you tell me how either of those pumps are currently better than my regulated setup right now. Flow is more than adequate and pressure is regulated to within spec. I’m not trying to cause an argument or anything but I fail to see how the Facet pump would help me here. Regardless I was talking to a couple of injection shops today and I’ll be planning to pull the pump out and pull it apart and do some investigating.

 

[asmith]

Two things first the facet pump is definitely not recommended anymore. Their quality has fallen off a lot and they really don't flow enough for our trucks.

Second I am not an IP expert but it sounds to me like something is messed up internally. 60+ psi is a big difference from 11 psi. I would be getting in touch with Justin at R+D to see if he can point you in the right direction as to what could be the issue.
Are you sure you have it regulated down enough now?

 

[BMadScientist]

I’ve been in contact with Justin, when I talked to him last week he had said that there probably wouldn’t be any issue inside the pump had I put 60 psi to it but it would just run like crap. I’ve put a new high quality fuel pressure gauge on the truck so I know what kind of pressure I’m getting out of the regulator and I can tell you for a fact the truck will not run with anywhere in 5-12 psi of fuel inlet pressure.

 

[IDIBRONCO]

Maybe you should try calling Justin again. I'm also no IP expert, but he is.

 

[BMadScientist]

That’s been my plan, I called his shop today and was talking to the Katie there for a little while but never got around to making another call to pick Justin’s brain.