Gradall 534C-6 Fuel Starting Issue

[John17three]

So, having some hiccups with the lift again. This time fuel related (I think).

Within the last 6 mos, I noticed while triggering the boom function at idle, the lift would die. Thought that was odd. Never done that before. I’d start it back up. Going forward, I just applied more gas.

Well, just in the last few weeks, I noticed that every once in a while, for no reason at idle, the engine would rev up, then back to idle.

Well, last week the frequency picked up. After getting a gable wall of my log home suspended on the side of the house, I shut it off. This time it would not restart. Turned over, but nothing. Then I realized it had been a minute since I put fuel in it. It was down to about 2.5” in the tank. So my neighbor came over after adding 10gallons.

He showed me the lift pump on the side, but it didn’t act like it did anything. No tension on the toggle arm. He took a few of the hoses off, checked for fuel coming through the line. He also cracked open one of the metal lines. Not sure what he was doing. Nothing work. Then he pressurized the fuel tank somehow with air. That didn’t work. We were at a loss what to try next. So then I decided to try some ether to see if it would kick off that way. Turns out it fired up!! Sweet! It idled as long as we needed it to finish the afternoon work (30 minutes maybe). I shut it off, then started it back up. All was well.

It sat a week.

I fired it up this afternoon and immediately actuated the boom. It died. Would turn over, but wouldn’t kick off. Then I sprayed some ether, fired up. Figured I was gonna get another experience like last week, but on my way across the pasture with the lift (to hang treestands with it), it started revving high again. Under full throttle it with the engine revs, this thing just frigging took off. well, that was short lived. I went through two small roller hills and I left off the gas to check a low tire real quick, and it died. This time, ether wouldn’t work.

Here are some unknowns: did the 10gallons fuel bring it to the standpipe and all I have is a fuel level problem? (I’m skeptical i used 10gallons idling for 30 minutes, but I suppose if that barely brought it to acceptable level, that could be the problem)

Or is that lift pump causing an issue?

I’m gonna replace that lift pump ($25 online), probably replace the fuel filters too.

Any other things I should consider?

Model: 534C-6
Engine: Cummins 4B39-C
Engine Serial: 45266866

 

[Delmer]

No, you have more than a fuel level problem.

The lift pump could be causing problems. IF the neighbor knew what he was doing, he should have easily seen if the lift pump was working. You have a new one coming, but we still don't know what's going on.

When I hear reving up and dying, it sounds like you're sucking air, which usually means you have a blockage and a suction leak. Or it could be a lift pump issue, I don't have experience with that, so I'll leave it to somebody else.

How about a description of the fuel injection pump? That matters more than the engine model if you're having fuel problems.

 

[thepumpguysc]

I just went thru this exact same thing this morning.. the lift pump hand primer would push & immediately go limp..
I filled the filter, bled the lines at the injectors & it would start & run.. run until the filter emptied {1/2 way}.. it would rev a few times & die..
I removed the filter refilled a few times & the same thing every time.. BAD LIFT PUMP..
The customer had an electric pump that I rigged & it fired up & ran fine until the new lp comes in..

 

[John17three]

Delmer, sorry, the lift pump was not working. No pressure at the connection to the filter adapter.

After removing the pump, it was immediately noticeable that the internal lever that actuated the diaphragm had come loose from the shaft.

I Put a new pump on. Got pressure now at the connection point where lift pump meets the filter attachment. Sounds like it working. We are gonna try and pressurize the system again, and see if that gets it jump started.

 

[Delmer]

OK, I misunderstood. So you and the neighbor kept trying to get it to run knowing the lift pump wasn't working.

 

[John17three]

OK, I misunderstood. So you and the neighbor kept trying to get it to run knowing the lift pump wasn't working.

We knew the manual lever wasn’t pumping, but wasn’t sure why. We pressurized the system with an air tank to get it to push fuel through the filters.

I edited my post above that explains why we later found out it wasn’t pumping.

 

[John17three]

Welp, turns out there was a gunky in-line filter between the tank and the main fuel filters. Aftermarket modification, evidently. We spliced it back together, and pressurized the system. A couple squirts of ether and got’er going. Runs fine. No revs like its getting air leak.

 

[Knepptune]

That’s not aftermarket. Every gradall has that little lawnmower in-line filter right at the back off the engine. You’ll want to put a new one back on there unless you want the lift pump to catch all that gunk. That’s the only filter between the tank and lift pump.

 

[Delmer]

If it's original, then it should be a strainer and you should be able to back flush it and put it back in place. DON'T put one in there that's made for gas or a fine filter for diesel. You need the oem, or a coarse filter/screen/strainer in that location.

 

[Knepptune]

Ye should be a course inline diesel fuel filter. Item 12

 

[Delmer]

Here you go: 150 micron, =.15mm =.006" so I bet it is a strainer, or a "cleanable filter".

https://www.dieselequipmentinc.com/products/p550974

 

[willie59]

Yep, diesel systems like this shouldn't use an inline "filter" prior to the lift pump, but one may find and inline mesh screen filter. The idea is to keep large debris from going through the lift pump. As for the fine particulates, let that pass through and get trapped in the main fuel filter.