Fuel Filter Only Half Full???

[Kicker_92]

We have an EX55UR-3 with the Isuzu 4LE1 engine that is having really rough starting. For the first couple of min until it warms up it has to be kept at 1/2 to 3/4 throttle just to stay running, with lots of white smoke / vapor coming out. It also seems to have a missfire at high throttle when warm.

I noticed that the fuel filter is only maintained about half full. The water seperator is full, but the fuel filter does not fill up even when sitting off with the fuel pump running. (these are the small ~3" filters in the see through canister)

Should fuel filters be full of fuel, or is this normal?

 

[watglen]

I've noticed the same half empty filter bodies, and they never affected the performance of my engines. Not sure why they have air in them though.

White smoke is unburnt fuel. I had a tractor that did the same thing for years. In the end the engine unknowingly recieved the wrong head during a rebuild, and had very low compression. It was finally diagnosed with a compression test, so i would start there to diagnose any white smoke problem.

 

[watglen]

I've noticed the same half empty filter bodies, and they never affected the performance of my engines. Not sure why they have air in them though.

White smoke is unburnt fuel. I had a tractor that did the same thing for years. In the end the engine unknowingly recieved the wrong head during a rebuild, and had very low compression. It was finally diagnosed with a compression test, so i would start there to diagnose any white smoke problem.

 

[Kicker_92]

Thanks, the white smoke is only for a couple mins after starting up, I think I might have a small headgasket leak thats contributing for it.

My concern is that the air may be moving into the injectors and causing the misfire at high thottle. Only about 1/3rd of the fuel filter is actually sitting in fuel.

I've tried removing the bowl, filling it with fuel and reinstalling, but no luck. Is there a way to purge the air from these systems?

 

[willie59]

If your filter or strainer is continually filling with air that's typically caused by a fuel flow restriction from tank. Many Hitachi machines have a strainer inside a banjo bolt fitting in the fuel line. Sometimes the fitting is the one that feeds the water seperator bowl. Seems I remember seeing another recent thread about a small Hitachi that had a strainer in the banjo fitting at the lift pump.

 

[Monrad]

If your filter or strainer is continually filling with air that's typically caused by a fuel flow restriction from tank. Many Hitachi machines have a strainer inside a banjo bolt fitting in the fuel line. Sometimes the fitting is the one that feeds the water seperator bowl. Seems I remember seeing another recent thread about a small Hitachi that had a strainer in the banjo fitting at the lift pump.

Yip i agree, that little strainer can really get clogged, find it and give it a blow out, prob wont hurt to put a new fuel filter in to if you havnt already.

 

[Wardiker]

If your filter or strainer is continually filling with air that's typically caused by a fuel flow restriction from tank. Many Hitachi machines have a strainer inside a banjo bolt fitting in the fuel line. Sometimes the fitting is the one that feeds the water seperator bowl. Seems I remember seeing another recent thread about a small Hitachi that had a strainer in the banjo fitting at the lift pump.

Yeh, that was my thread, the banjo bolt strainer was in the one by the lifter and most awkward to get at (but not that hard). In the end it was clear and the problem was a clog in the fuel line near the tank, we removed the tank and pressure washed it, someone had replaced 8 inches of fuel line and the clog accured when they connnected the old and new together (they over heated the old line and melted it) Ive also seen that the bottom of the tanks have so much crud in them that the connection there gets clogged were the line connects to the tank.

 

[Kicker_92]

Finally got a change to work on the machine today so here's what I've found:

- Drained the fuel and pull out the pickup fitting per the other thread, and there was no screen there. (looks like it's been removed)

- Fuel coming out looked good, no signs of water settling out.

- Still starts very rough, needing close to full throttle just to keep it alive for the first couple seconds.

- Lots of air bubbles in the water seperator and fuel filter when its running. After shutoff they both full up to full, but drop to about half full in the fuel filter while running.

I'll try to attach some photos, any suggestions on where else to look for a strainer or clog?

 

[watglen]

Air getting in on the suction side of the fuel pump????? Cracked fuel line somewhere????

 

[Aardvark]

half full

noticed the same thing on my Ex 5.8 mu once or twice before, long time ago.
I replaced the thin o-ring between glass (plastic) bowl and housing as I suspected that it could bee sucking air there.
Also the elbows where the lines come in & out have only got a very small O-ring (could even be a fibre gasket from memory).
I've actually had two of these elbows pop out on the inlet side (on different machines)
Ended up replacing the one on the 5.8, changing it for a spin on cartridge style out of frustration:bash before I found the blocked strainer.:Banghead
Thought it was kind of pissy in size for a 2 litre engine anyway.
Having said that I've seen larger strainers on on lawn mowers to BTW

 

[Aardvark]

pump

Don't know about your digger but my 5.8 has an electric pump so purges it self

 

[Kicker_92]

This machine is a 1999, and it must have an electric pump because the fuel starts circulating as soon as the key is turned on.

This is the first diesel I've worked on, so please forgive my ignorance. It's pretty hard in there to figure out where each of the lines run.

- Does the fuel go through the pump and then the filters, or are those filters on the suction side of the system?

- If the pump self purges, is there a vent or outlet that could be clogged and not letting the air release? I've let the pump run for a while without starting and it just seems to circulate the fuel without removing the air.

- Would the air, or lack of fuel pressure cause the hard starting symptoms above?


Thanks again for eveyones help

 

[Kicker_92]

One more thing, what do the screws on the top of the filters do?

 

[willie59]

Kicker 92, did you catch what Aardvark said? When you remove those nut rings that hold the stainer and filter bowl in place and drop the bowls, there is should be an o-ring seal at that lip ring near the top of the bowls. Are those o-rings in place? And the elbows at the housing can come loose as he mentioned as well. The electric fuel pump "should be" after these filters, but I can't say that for sure. The fuel should flow to the housing on the left first, that's the water seperator bowl, then it flows to the housing on the right, that's the filter bowl, then it should flow to the fuel lift pump (elec pump), then to the injection pump on the engine. The shut off levers on each housing allows you to turn off the fuel flow when servicing filters. The screws are for bleeding air from the housings. If you have a relatively full fuel tank, you can open the screws and gravity will purge the air from the bowls. What is the lever valve to the right below the right filter? One thing you could try is to remove the filters from the fuel circuit. I can't tell what size fuel hose you have, let's say it's a 5/16" fuel hose. Purchase a clear plastic 5/16" in-line fuel filter, like a Hastings GF2P. Disconnect the hose on the left of the left filter housing, disconnect the hose on the right of the right filter housing, and connect the two hoses together with the in-line filter. Now try you engine and see what result you get.

 

[Kicker_92]

there is should be an o-ring seal at that lip ring near the top of the bowls. Are those o-rings in place?

Both filters O-rings are there and appear to be in good shape. One of the elbow fittings had worked loose a while ago, and is now sealed with epoxy into place.

The electric fuel pump "should be" after these filters, but I can't say that for sure. The fuel should flow to the housing on the left first, that's the water seperator bowl, then it flows to the housing on the right, that's the filter bowl, then it should flow to the fuel lift pump (elec pump), then to the injection pump on the engine.

So if these are all on the suction side of the system, I should be able to remove the last hose going out from the fuel filter, extend it into a clean jar of diesel, and bypass this whole system? That should let me test if it's an air leak causing the starting / smoke problems.

What is the lever valve to the right below the right filter?

That's the tank drain. I used it to drain all the fuel before removing the bottom pick-up fitting. Not much water of debris coming out leads me to believe it was cleaned sometime before I got it.



I'll try the bleeder screws on each filter to get the air out, then see if it comes back. If it does, I'll try bypassing the filter system on Thursday with a fresh can of diesel and see what happens.

 

[willie59]

Quote Kicker 92:

So if these are all on the suction side of the system, I should be able to remove the last hose going out from the fuel filter, extend it into a clean jar of diesel, and bypass this whole system?

"If" they are on the suction side. I don't know that for sure. The fuel path I laid out is my guess as to how it goes. Check your system, assuming the electric lift pump is after the filters, then yes, removing the hose from the filter that feeds the lift pump and placing it in a clean container of fuel should get you going for a test run.

 

[Komatsu 150]

I would also think you're pulling in air. If you run out of ideas shaving cream on any fittings, elbows, etc. will find suction leaks. And yes it's possible to suck in air and not leak fuel when shut off. Learned this the hard way.

 

[Tinkerer]

You certainly are pulling in air. I ran a service truck for seven years and this is the way I used to find leaks and also prime the fuel system from the tank to the injectors. Remove the fuel tank filler cap. Wrap a rag around an air hose gun. The purpose of the rag is to seal any air from escaping around the filler hole.Now very carefully inject air into the fuel tank while holding the air hose into it. Be very carefull with the pressure , 2 to 4 pounds of air pressure is plenty. If the fuel volume is low doing this unhook the fuel line on the tank outlet and inject air into the tank while being certain the fuel tank cap is off. Doing this will dislodge anything that may be plugging or partially plugging the fuel tank outlet. This is a temporary solution if it works because the garbage has to be removed from the tank if that is the problem.It was quite normal to find all kinds of garbage in fuel tanks , especially scrapers. Rags were a common problem (temporary fuel filler cap that fell into the tank). Weeds were another pretty common thing to find in a fuel tank. I guess the operators would check the fuel level with a weed and sometimes drop it in or a piece would break off.

 

[Kicker_92]

Worked on the machine last night. The source of the air seems to have been the water seperator O-ring, I'd tightened it as much as I could by hand, but I guess it still didn't seat.

Used a strap wrench to crank it on tight, and then was able to remove some air with the top bleeder screws on each filter. I had to turn it on to run the pump, then crack the bleeder screws about four times before all the air was released.

It's now running much better at high throttle, no more missfires. The hard starting symptom and white smoke is still there though, I'm wondering if I would need to purge the injector lines? The smoke come out in puffs, like one of the cylinders isn't firing right away. The smoke goes away after about 1-2mins warm-up.

 

[bilshatri]

Hi Kicker 92,
What I believe the fault you have is, the fuel system has been contaminated with water. This has caused your Injectors to fail. If you loosen all the injector lines and move them away from the injectors. Crank the engine over with you finger over the injector fittings, one at a time. See if you can feel any pressure on your finger. What I would recommend, is to replace or recondition your injectors. Hopefully, this will cure your poor cold starting. Please let me know, if this fixes your nightmare. Good Luck!