air in fuel line

sam un ont · May 14, 2016

I need help. I have a 426 cat backhoe with the perkins 4-236 engine. For a few years now the unit would just quit after a few hours and I would bleed the air out of the system and it would start. Lately it is getting much worse. The injector pump was sent out and tested so I know it,s good. I have been off and on for a year trying to find the source of the air to no avail. The tank has been taken off and cleaned and the pickup line checked. One thing I have noticed is that lately when it is initially put under load there is no sign of black exhaust smoke.Fuel pump has good inlet suction but seems weak on the out put side so that is my next step

This thing is going to drive me to drink whiskey right out of the bottle so pls. help

Sam

Dieseltech · May 14, 2016

Perkins uses a constant bleed orifice fitting on top of a filter base that's also hooked to the injector top return line back to the tank. May be a straight orifice or a banjo bolt, make sure it's not plugged. It's there so any trapped air that gets to the filter has a way out. If it's plugged the air then goes to the injection pump and kills the engine. Also make sure if NAPA/Wix filters are used the filter top outer groove does not have an O ring in it by mistake, that's the filter inlet. If blocked with the O ring the injection pump can't get the fuel it needs, even with a good supply pump.

sam un ont · May 14, 2016

I will check out those things, hopefully tomorrow. Right now when bled the tractor will idle it seems all day but when it starts to work it will run maybe 20 min.

Sam

Nordic · May 15, 2016

(quoted from post at 08:45:20 05/14/16) I need help. I have a 426 cat backhoe with the perkins 4-236 engine. For a few years now the unit would just quit after a few hours and I would bleed the air out of the system and it would start. Lately it is getting much worse. The injector pump was sent out and tested so I know it,s good. I have been off and on for a year trying to find the source of the air to no avail. The tank has been taken off and cleaned and the pickup line checked. One thing I have noticed is that lately when it is initially put under load there is no sign of black exhaust smoke.Fuel pump has good inlet suction but seems weak on the out put side so that is my next step

This thing is going to drive me to drink whiskey right out of the bottle so pls. help
Sam

Is the pick up line steel or rubber? On two of my big diesel trucks it turned out to be the pick up line after all (in the rubber section). Another truck had a pinhole in a Baldwin fuel filter and that would load up on air. Does your fuel pick up line come from the bottom of the tank externally or is there also an internal pick up line inside the tank?

NCWayne · May 15, 2016

Is it one of the turboed Perkins engines with the flame start element? If so, try changing the flame start element out.

I had one of the 3054 CAT engines (Perkins in CAT garb and name only) years ago that had a similar problem. I just about pulled my hair out trying to figure out the problem. Turned out what was happening was the little valve in the flame start element was letting air through it. As turbo built boost pressure, and it reached a certain point, it put just enough air into the system to cause the engine to shut down. Once dead, and restarted, the pattern would repeat. I changed the element when I got the problem figured out, and had no more issues.

Good luck.

sam un ont · May 15, 2016

First of all thank you for the help' With regard to your comments;

!/ The pickup is a steel line that enters externally along with the return at the top rear of the tank and is steel on the inside and it was checked when the tank was off for cleaning

2/ the engine is non- turbo and uses a ether shot system for cold start
Keep the ideas coming
As I stated it all started maybe 2 years ago when it might run for 2-3 days then just quit as if the key were shut off. I would then bleed it and be on my way but it has steadily been getting worse. the unit runs great when running and other than this is a great starter

Sam

shugy368 · May 15, 2016

I may be completely out of my league here but I've owned many diesel powered sailboats and once had a similar problem, At sea no less, 900 miles from anywhere. What I finally had to do was pressurize the fuel system which was no small feat, then follow every inch of the fuel system and lo and behold there was fuel being pushed out of the outflow side of the filter, trim the hose re-clamp and I had an engine again, which helped a lot at our next landfall!

shugy368 · May 15, 2016

I may be completely out of my league here but I've owned many diesel powered sailboats and once had a similar problem, At sea no less, 900 miles from anywhere. What I finally had to do was pressurize the fuel system which was no small feat, then follow every inch of the fuel system and lo and behold there was fuel being pushed out of the outflow side of the filter, trim the hose re-clamp and I had an engine again, which helped a lot at our next landfall!

shugy368 · May 15, 2016

I don't understand CV-post SAM UN ONT?

shugy368 · May 15, 2016

SORRY I MUST HAVE HIT THE POST BUTTON TWICE, I don't really stutter

AJ. · May 15, 2016

Have you cleaned the gauze filter in the feed pump,if not do so,its under the dome shaped cover held on with a single screw,while there check both the inlet and outlet pipe are not squashed close from overtightening.
AJ

sam un ont · May 15, 2016

I have had the lift pump off and inspected numerous times and found nothing amiss. However due to the fact that I could get about 15 lbs. of suction on the inlet side of the pump and only about 3 lb. output I am beginning to think that maybe one of the pump check valves is leaking. In any case I have a new pump coming in tomorrow and we shall see what happens In the meantime thanks for the help and keep those ideas coming in

Sam
P.s I do not understand your query about my cv post Shugy 368

shugy368 · May 15, 2016

Sorry I did'nt understand that was a default in the posting process. Glad you got your problem fixed, or did you?

sam un ont · May 17, 2016

I think that I may have found my answer. I got the new lift pump and bench tested it and there was good suction and it would shoot fuel 6 feet. Great I thought. Put the pump on the engine and had some one crank it over while watching
the output port and there was very little. I then really inspected the arm of the old pump and it was only worn on one side so I suspect a worn camshaft lobe as I can not think of anything else.

Any ideas , I am leaning towards an electric pump

Sam

sam un ont · May 17, 2016

If the answer is to use an electric pump I was thinking of making up a plate and just remove the pump completely

Sam

air in fuel line

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