Why is the axial Standyne injection pump used on our engines so hard to prime? Let me put this into context: maybe a month ago I had a no start condition that I diagnosed as either a failing lift pump or an air infiltration problem. I replaced the lift pump and got consistent starts but sometimes it would require extensive cranking to start. I ordered the return line kit and double checked my glow plug system - all eight plugs read 0.5 to 1.0 ohms and the controller seems to be cycling correctly.

My return line kit arrives and this past Sunday I had a chance to install it. The truck seemed to start fine a couple of times after that but when I went to go to work Monday morning the truck would not start. It required the 200 amp battery booster and about a minute of total cranking to get it to take off. Same thing when I went to leave work later that day.

Given that the only thing I changed between the occasional hard start and the no-start were the return lines and o-rings I figured I had an improperly seated cap or defective fuel hose. I checked all of this and found one suspect spot (wetness on two injectors) so I replaced the hose there and re-seated the caps. I also wanted to eliminate anything before the IP/return line plumbing so I installed an electric transfer pump and bypassed my brand new lift pump.

This morning I run the new electric pump for a while before attempting the start to make sure there's no air in the fuel but the truck will not start without lots of cranking and the booster. This evening after work I think I identified a spot where air was getting in (loose connection on the return line coming out of the IP) and fixed that, I will wait another hour or so then see if it starts.

This leads me to my question: what is it about the design of this IP that makes it so hard to prime? Even if the return lines are draining the pump due to an air leak my electric pump should be re-priming it because it is not turned during the no-fuel condition, right? I've been working on diesels since I was 14 and I've never seen anything even remotely this obnoxious (other than cracked liners, a thrown rod, and anything made by John Deere). I've even chased this air leak problem on other 7.3s but neither of those gave me even remotely this much grief. Maybe my IP is bad? The fact that the problem got worse after disturbing the return lines contradicts that though...

Any insight would be much appreciated!

 

My truck was like that. I had some simple line problems but it seemed like after I got the air out of it it still didn't want to start. About a month after that the injection pump started leaking fuel everywhere, I replaced it and now even if I run the truck completely out of fuel, I can switch tanks and spin it for 20 seconds and it will be running.

By the way, I see you have a 1962 Ford with a 453, thats pretty cool, I have a `1985 Chevrolet 1 ton with an aluminum 353 Detroit out of a Marine Gamma Goat, bolted to the Chevrolet Tranny, not a powerful truck, but gets good mileage.

 

The electric pump cannot force fuel through the injection pump, through the injectors, and back to the tank.

We are lucky this system purges itself at all. I have worked on equipment were the injectors do not have return lines, and the engine will refuse to fire unless you crack the high pressure injection lines.

 

If it has enough pressure it will help alot if it is pumping while the engine is spinning plus it will also fill the injection pump up, all the way up to the top of the pump and start pumping out the return line at the top.

 

Andy: Yeah, the 4-53 F250 is a hoot. Its gets 17 MPG and its exhaust noise can drown out semis on the Interstate. I hear that the aluminum gamma goat motors can be trouble, any truth to this? Interesting thought on the IP, maybe mine is on its way out. i have confirmed that my electric pump will make fuel come out the return line on the top of the IP without the engine running.

Dave F: In my experience with axial pumps (mostly Roosa-Master or derivatives) once you get fuel at the bleed nut on the IP body it can push the rest of the air out, even if the injector lines are dry. My thought was that there's maybe some place in the pump where air can be trapped, where having a bleed nut would be helpful on our pumps?

Anyway, I just tried it after addressing the latest air leak (loose clamp on the IP return line) and letting it sit and....it started! Tomorrow morning I should know for sure.

Thanks guys!

 

You can't drive mine on the interstate, well you could if you were happy going 55 down the interstate. I put a straight pipe on it at first, but I couldn't sit in it without ringing my ears off. I'm glad it doesn't have a radio because you couldn't hear it if it did. Never had a problem until a few days ago, the top radiator hose came off and I couldn't see the temp gauge because it was dark outside and the lights in the cab don't work, by the time I got home I shined a flashlight on it and it was at 235 degrees, now if you start it it blows water out around the radiator cap, I hope its just a head gasket but it may be the fire ring on the pistons. Good luck to you on your air problems, My 88 gave me hell over that for about a year, it took me forever to get through it. One thing that helped a lot is when I bypassed the lift pump and installed a pump off of a 99 Powerstroke, it has more pressure than aftermarket pumps you buy, works great.

 

The problem is a return line air leak breaks the vacuum that holds the fuel above the tank level.

If the leak is bad enough, the entire fuel system will drain back.

When you go to start the engine, the amount of fuel injected is so small, it takes a long time to force even a little air through the system and out the injectors.

 

The plot thickens! I met up with a few other guys who have IDI 7.3s and 6.9s after work today and we discovered that one of my batteries is toast. I replaced both with the highest amp batteries Napa would sell me that would fit in the pans, I'll know if low cranking speed and/or low voltage to the fuel cut off solinoid was the problem tomorrow morning...

Incidentally, all of these guys have had air intrusion problems on all of the 6.9/7.3 motors they own, and those who also have 6.2 and 6.5 Chevies have not had this problem at all.

 

Power Strokes as far as I can tell don't have this problem either.
And I've never heard of a Cummins with this problem either, they only have air-intrusion when someone installs the fuel filter wrong.

It seems to be an IDI thing, the only thing I hate about these trucks/motors.

 

I just went out to start it and see if yesterday's festivities fixed it and....it started right up! If you're searching this forum on air intrusion or hard start problems, remember to check your batteries and starter! It sounds obvious in retrospect, but with the engine cranking and starting when warm and the previous fuel symptoms I had totally overlooked this possibility.

 

Glad to hear you got it worked out chevenstein. I got a question for yall that I think may fit in this thread. I had a problem similar to this last winter (just bought my truck summer 07) and went through the glow plug problems and just resently got 2 new batteries. The truck has been starting just fine even down to 16deg until yesterday. It started fine, ran 5 sec and died and wouldnt start back just like last winter. Any way my question is, could cold weather make an air intrusion problem worse? And would it go away when the weather warms up?

 

Running briefly then dying and not starting was my original symptom, which replacing the lift pump resolved for me. You might also want to examine the return lines for cracks or wetness from leaks, or just replace them and the o-rings if they're old. What might be happening is the o-rings are old and have shrunk and the cold weather is making them shrink more, which lets air in. Good luck!

 

smokey98, juss wondering if you use a fuel treatment to prevent your fuel from gelling? That is cold enough to gel diesel.

 

Yeah, all the rubber lines under the hood still have paint on them so aint no doubt they need replacin, huh. That will be my next project.
As far as anti gel treatment, nope havent even thought about that even know I have a can of it on the shelf in the basement. Thanks guys