Perkins air in fuel

[GManBart]

So about a week ago I was using my Massey 241 to clear the last (I hope) snow of the year, and it started running a little rough, the idle jumped about 150rpm from it's usual, and while I was heading back to the barn, it quit. On a whim I used the prime lever on the lift pump, and that got it started, but it quickly quit again. I did maybe 75 strokes on the prime lever, and was able to get it restarted, and running long enough to back it into the barn.

I figured the fuel filter was clogged, but the sediment bowl looked clear. I put a complete new filter assembly on it because the old one had dried seals, and I was an idiot and broke the glass bowl on the original one (it's about the same price to buy a filter and glass bowl as a complete assembly). I got it all back together, followed the instructions for purging air from the system, and checked the air filters (blew them out with compressed air) while I was at it. The engine started and seemed to be running okay. I let it idle for maybe 20min while I was cleaning up, then decided to run it up and down the road for a few minutes just to make sure it was running fine. I went a bit less than half a mile, turned around, and came back...the whole time in high gear at wide open throttle. Things seemed okay until I closed the throttle, and turned into the driveway....the engine quit. I ran about a hundred strokes on the prime lever, and it started, then quit...did that a few times until I got it running long enough to jump on, increase the RPM, and get it in gear.

After I got it back in the barn I looked over all the fuel lines from tank to pump, to filter, to injector pump, and then noticed there were air bubbles in the filter sight bowl...big ones. I got the engine running again, and cracked the #1 and #3 injectors...pure foam coming out, but it was running. I could watch new bubbles get drawn down through the bottom of the filter elements, and then up into the center, so clearly it's sucking air somewhere between the filter and the pump. I checked the oil in the crankcase, and it's normal, no signs of fuel.

Could the seal/diaphram be leaking in the lift pump enough to let air in, but not put any fuel in the crankcase? The lift pump looked like it was a little wet around the cork seal that divides the top, and bottom...but there's been a lot of fuel sloshing around the whole area while I was working on it over the past week.

I didn't see any spots where the fuel lines appeared to be wet, or fittings that were loose, so I'm considering just trying a new lift pump next.

For reference, the engine is a Perkins 903.27 with less than 1400hrs on it (late 1999-early 2000 production).

Thoughts?

 

[murphy1244]

your sucking in air someplace, spray some wd 40 over the lift pump and see what that does.

 

[GManBart]

your sucking in air someplace, spray some wd 40 over the lift pump and see what that does.

Good idea on the WD40!

 

[DT86]

Check lines pre lift pump for rubbing against brackets, ect.

 

[GManBart]

Check lines pre lift pump for rubbing against brackets, ect.

I did check that quickly, but will do a better job tomorrow.

Tried the WD40 trick....didn't see anything unusual.

 

[banjodunn]

G'day check the tank line for blockages maybe there is something floating around the pickup.


Jon

 

[Tx Jim]

I agree check for good fuel flow from tank. Is tank vent plugged?

 

[GManBart]

I agree check for good fuel flow from tank. Is tank vent plugged?

It certainly can't hurt to check that, but if I'm getting lots of fuel flow at the injectors, how would it be causing the problem of air in the line?

 

[GManBart]

I didn't have time to disconnect the fuel inlet at the lift pump, but I checked all the supply, and return lines/fittings, etc and they all look fine. A couple of the fittings weren't as tight as I'd like, but nothing changed after tightening them. It'll start, and run, but it's sucking large bubbles down into the filter sight bowl. I tried spraying WD40 on all the connections, and didn't notice anything unusual.

Anybody know anything about the seal/diaphram configuration on the lift pump? Could it be sucking air into the lift pump, and not putting any in the crankcase sump?

 

[MHarryE]

It is possible. That lift pump is not the most robust. It may be possible that the FIP has enough draw at full speed to draw enough fuel to run at but at lower speed it needs help. Grasping at straws here. I think the same lift pump was used, and possibly is still used on unregulated engines, across the board. The only way I know to test for sure is to replace but dealer mechanic may have advice.

 

[doxford jim]

Fuel injector return lines ? Any signs of fuel around the heads from fuel lines?

 

[GManBart]

It is possible. That lift pump is not the most robust. It may be possible that the FIP has enough draw at full speed to draw enough fuel to run at but at lower speed it needs help. Grasping at straws here. I think the same lift pump was used, and possibly is still used on unregulated engines, across the board. The only way I know to test for sure is to replace but dealer mechanic may have advice.

That makes some sense. For all of $26.02 I ordered a new lift pump today...figured it's worth a shot. I'm still going to disconnect the fuel supply from the tank to the lift pump, and see what that looks like first. I can't see where the outlet is inside the tank, but the areas of the tank I can see with a super bright flashlight look extremely clean.

 

[GManBart]

Fuel injector return lines ? Any signs of fuel around the heads from fuel lines?

I looked at the return lines more closely tonight, but didn't see any signs of fuel coming from them. Granted, I had already tried bleeding the lines by loosening the injector fittings, so there was fuel all over the general area, and I could have missed something. Before I loosened the injector fittings the entire area was dry, and free of fuel.

 

[Oldtractorfixer]

Problem is probably at or before the lift pump. After the pump it should all be under pressure and would leak not suck air. Before the pump is the vacuum side which can pull in air. Will not necessarily leak fuel. A restriction pre-pump can create a high vacuum in the suction line making an air leak more likely.
Good luck.

 

[GManBart]

Problem is probably at or before the lift pump. After the pump it should all be under pressure and would leak not suck air. Before the pump is the vacuum side which can pull in air. Will not necessarily leak fuel. A restriction pre-pump can create a high vacuum in the suction line making an air leak more likely.
Good luck.

That makes perfect sense....thanks. I'll start with the line from the tank to the lift pump, and see what the flow looks like next. I'm not terrible worried at this point, but it was kind of funny when my wife said "maybe your second tractor should be a new tractor too?" last night....gotta love that woman!

 

[sd455dan]

That makes perfect sense....thanks. I'll start with the line from the tank to the lift pump, and see what the flow looks like next. I'm not terrible worried at this point, but it was kind of funny when my wife said "maybe your second tractor should be a new tractor too?" last night....gotta love that woman!

If the fuel system proves to have good volume from the tank,

Had a somewhat similar problem on Leyland 344, the person that worked on it before me replaced the fuel filters , the old filters were dirty for sure , the system could be primed up and the tractor would start and run for a bit and then die. figured it needed a new pump- the linkage on the pump was very worn -installed it and went on to the new filters- in the end it was a small leak on the installation of the o ring/ filter housing allowing air to be drawn in.

When trouble shooting, we found the filters were virtually empty.

The weird thing was that this tractor had the fuel tank mounted ABOVE the engine- but it was level with the filter housings... and with a leak at the filter housings the injector pump would empty the filters even with a a full tank of fuel and a brand new lift pump. This was a CAV injection system and the engine was BMC. Not sure if the Perkins is the same.

Good Luck- I'm sure you will get it running well

 

[GManBart]

If the fuel system proves to have good volume from the tank,

Had a somewhat similar problem on Leyland 344, the person that worked on it before me replaced the fuel filters , the old filters were dirty for sure , the system could be primed up and the tractor would start and run for a bit and then die. figured it needed a new pump- the linkage on the pump was very worn -installed it and went on to the new filters- in the end it was a small leak on the installation of the o ring/ filter housing allowing air to be drawn in.

When trouble shooting, we found the filters were virtually empty.

The weird thing was that this tractor had the fuel tank mounted ABOVE the engine- but it was level with the filter housings... and with a leak at the filter housings the injector pump would empty the filters even with a a full tank of fuel and a brand new lift pump. This was a CAV injection system and the engine was BMC. Not sure if the Perkins is the same.

Good Luck- I'm sure you will get it running well

That's good stuff...thanks!

 

[GManBart]

Disconnected the input fitting from the tank at the lift pump tonight and it seemed to be perfect fuel flow....solid, steady, no sign of bubbles. I guess I just wait for the new pump to get here

 

[D7E]

Lift pump probably . Have had similar problems on combines with 6cyl perkins engines and filter heads that hold the filter have been to blame .

 

[GManBart]

Lift pump probably . Have had similar problems on combines with 6cyl perkins engines and filter heads that hold the filter have been to blame .

Well, I have a new lift pump on the way, and I put a brand new filter assembly (with new head) on it the other day. If the lift pump doesn't fix things, I'm going to take the new filter head off, and put the old one back on, with the new seals, to see what happens.