Need Help with Fuel System Problem

[ColinR]

I have a 1986 Volvo 2002 2-cylinder diesel that ran well until yesterday, when I decided to change the filters. It has a Racor primary filter, which takes a 2000sm cartridge, and a spin-on filter on the motor.

I replaced both filters, topping up the Racor with diesel and installing the spin-on filter dry. I then tried to bleed the system by loosening the bleed screw on the secondary filter and pumping the fuel pump lever. After a thousand or two pumps, nothing. The secondary filter was still empty. I changed the Racor again with new gaskets, but still couldn't bleed it. I filled the secondary 3/4 full with diesel, tried again. No luck. However, the engine started and ran well. I was concerned that the fuel system still had air in it, so I loosened the bleeder screw on the secondary with the engine running, and no fuel or bubbles came out. I shut down the engine, removed the secondary filter, and it was still 3/4 full.

Logic told me that there must be air getting in the system between the tank and the fuel pump. I disconnected the fuel line at the tank and blew into it. I couldn't find any diesel or air leaking, and it pushed some fuel into the secondary filter which was now 7/8 full. I bypassed the Racor, changing the flexible fuel line being careful with connections. No change. I removed the bleeder screw, put my finger over the hole and pumped - no apparent sign of pressure. I then applied suction to the bleed screw and managed to fill the secondary filter. But now the engine wouldn't start.

So I loosened fuel connections at the injectors to bleed them, but no fuel came out. Turned up the decompression lever, closed the engine through-hull, and cranked. And cranked.... No fuel.

If crack open the bleed screw on the filter and pump, I don't get any bubbles or fuel. If I unscrew the bleed screw most of the way, fuel starts to come out so the filter is finally full. But no fuel to the injectors.

I'm at my wit's end. Does anybody have any idea what's going on? It almost seems like the fuel pump isn't working, but it is hard to believe that it failed in the middle of a filter change.

[bobconnie]

Im not to sure ! But ALWAYS FILL THE FILTERS FULL !! and I mean always cus this is what happens everytime you try to suck fuel thru a less then full filter !! I have always installed a electric fuel pump at or as near as possible to the fuel tank and still fill the filters full by hand before trying to pressure the system with the electric fuel pump ! Then ya get instant start and seldom need to bleed anything! Ya still have an air bind problem keep pumping fuel even if ya have to use a hand bulb to fill it !! Just a thought

[suncoast sailer]

Hey bud, I am at work wil read more into it later, first though is lift pump not working good, if you have foot pump or air compressor try to put air pressure into fuel tank not big heaps but enough to push fuel down line to fill filers and all way to the pump, hope that works

[levm]

It is possible that the transmission pump went bust a while ago but as long as the lines were full of diesel the engine kept working fine.
Most likely the fuel line from the tank to the engine is full but the line between the engine filter to the high pressure pump has air in it.
My recommendation is to repair the transmission pump and then bleed the lines all the way to the injectors.
I will use the improvisation of air pressure into the fuel tank or a hand bulb pump only if I have no other option. Your best bet is to fix the transmission pump and do the bleeding right.
An electric transmission pump between the Racor and the engine is a good idea. I have one on my engine and it saves me a lot of grief.
Good luck.

[Stu Jackson]

If you've been cranking for so long, make sure your muffler isn't too full.

[tpkas]

Hi ColinR,

I've just replaced both the primary and secondary fuel filters as you have on two 20hp 3 cylinder volvos. I was able to refill both the filters (from completely empty) using only the manual pump and bleeding at the bleed screw. It did require a fair bit of sustained pumping but it did work.

You checked for pump pressure by removing the bleed screw and placing your finger over the bleed and found no discernable pressure .... because of this I'd be inclined to agree with Suncoast Sailor and suspect your lift pump.

Good Luck.

PS I have shut off valves at the fuel tank whick I close before changing the filters .... If I hadn't opened them prior to bleeding I suspect the symptoms would be similar.

[gjordan]

Lift pumps on most engines are drivin by a lobe on the cam, and if that lobe is in the full up position when you are trying to pump with the lever , you wont get any action. Some engines tend to stop at the same point in their compression cycle every time, and if that happens to be when the pump lobe is fully up you might have trouble more than one time. If as you said, you pumped many times and got nothing out of the filter bleed screws, then rotate the flywheel 1 revolution and try again. If that doesnt work try removing the line at the outlet of the lift pump and check it there. If the pump doesnt work at that point I would block it off and buy an electric fuel pump from an auto parts store and by pass the original. I have had lots of problems with lift pumps and on my last 2 Perkins I have gone to 12 volt pumps. I always carry a spare but never used the spare. By the way, if there is still air in the body of the injection pump, cracking the nuts at the injectors wont bleed it out. Good Luck with it. Let us know how it works out.____Grant.

[ColinR]

Thanks for the feedback. I did try moving the cam position several times, and I took the precaution of shutting the water intake before cranking.

"if there is still air in the body of the injection pump, cracking the nuts at the injectors wont bleed it out" - the injection pumps are lower than the oil filter, so I assume that the engine ran earlier while I was having bleeding problems due to gravity feed on the injection pumps. So if they are now full of air, how do I get fuel to them? If I manage to pressurize the fuel system, will it push fuel to the injection pumps? I'm concerned that I'll damage them by running them dry.

[Florida Mike]

Start off by disconnecting the discharge fuel line at the lift pump, operates upon by hand check for fuel flow and pressure. When that works reconnect the line and move to the filter same procedure. When that works moved to the injector pump and crack the line until you get no bubbles. When that works move to the injectors and crack them until you get fuel flow and no bubbles. If your engine adds compression release you can relieve the compression and use a starter instead of hand pumping. If not you will have to bar the engine over until you get pressure on the priming lever. Several friends with small diesel’s use an outboard motor priming bulb matted somewhere between the first fuel filter and their lift pump. Just my two cents, Mike.

[Tynesider]

Originally Posted by ColinR

Thanks for the feedback. I did try moving the cam position several times, and I took the precaution of shutting the water intake before cranking.

"if there is still air in the body of the injection pump, cracking the nuts at the injectors wont bleed it out" - the injection pumps are lower than the oil filter, so I assume that the engine ran earlier while I was having bleeding problems due to gravity feed on the injection pumps. So if they are now full of air, how do I get fuel to them? If I manage to pressurize the fuel system, will it push fuel to the injection pumps? I'm concerned that I'll damage them by running them dry.

Hi Collin
I Had problems a few years ago after refitting new filters, my engine started but every 4 hrs just stopped, bled the engine then it would run another 4 hrs then stop again.

I spent weeks trying to find an air leak in the pipework, replaced the lift pump, changed the fittings etc etc.

Then some bright spark said did I know I had installed the new filters higher than the old filters in relation to the fuel tank, I lowered the filters so they were 'gravity' fed and problem solved ever since!

Might be worth a check!

Mike

[gjordan]

Collin, If the filter is lower than the tank and the injection pump is lower than the filter, then gravity should get enough fuel thru to bleed the system. Obviously that hasnt worked. If the lift pump checks out and you get the bubbles out of the filter, then make sure you get the bubbles out of the injector pump housing. There are usually 2 bleed points on the pump housing and if you dont get the air out of both of them, the pump wont build up pressure to the injectors themselves. That is why I said it wont do any good to crack the nuts at the injectors unless the rest of the system is bled first. If you have clean fuel coming out of the bleed points on the pump itself, then crack the nuts to see if it is getting to the actual injectors. Good Luck.____Grant.

[ColinR]

Thanks to all who responded, a lot of useful information. I disconnected the banjo bolt on the input side of the lift pump, and operating the lever doesn't generate any suction input side or any pressure at the bleeder screw. So it appears that the pump is dead. The engine was probably running on gravity feed siphoning the fuel until I broke the siphon by replacing the racor filter. Next step is to replace the pump, and then bleed the system using the forum's advice.

Colin

[sartorst]

This happened to me once,and after hours of searching found the plastic plug for other fuel line options in the racor had cracked

[Chuck49]

I tried to read all the post, and see if anyone had suggested checking your filter gaskets. If one is missing or cracked or not seated correctly, or one of the gaskets are doubled, it will suck air. I have seen all the above happen, and is so easy to overlook. If you have not check this, do so before replacing the pump. At least, give it a try, if you haven't already. Even take a mirror and check the gasket seat, and make sure nothing is in the seat, that is not suppose to be there, if you can not see the seat.

[Irish rambler]

I once had a similar problem on a Perkins lift pump, after stripdown I found the non return vlave in the lift pump was loose and causing the pump to 'pant', being away from base I cleaned it with solvent, carefully applied Araldite to re bed the non return filter, that was about 12 years ago, I bought a spare but the original is still working fine. I hope this helps someone. happy cruising.