300Tdi reduced power. Is it imminent lift pump failure?

[Troll Hunter]

As the title. I replaced the fuel filter and lift pump last October, using a Wix filter and a Delphi unit. I've done about 10,000km since then, but have recently been losing power intermittently for no obvious reason. Today I was flat out at 60kph, on the flat!

I've just replaced the fuel filter, again, but it doesn't appear to have made any difference. When I opened the vent on the filter body with the engine running no fuel came out, suggesting to me that the pump is on its way out. I don't have a replacement pump available. How can I test performance of the lift pump?

I'm sure this has happened to other members, so all ideas, suggestions and experiences will be gratefully received. Many thanks, in advance,

Mike

[mike4444244]

To test the pump, take the outlet off and either pump the manual priming lever (if it's same as 200) or turn the engine over, fuel should pump out, if the diaphragm is split it may just trickle out

The other test is to gravity feed diesel straight from a jerry can or similar straight to the FIP, if that cures your problem you know the pump is faulty

Mike

[CwazyWabbit]

BTW if trying the manual priming lever it won't work if the engine is at the point in it's rotation where it's already pressing the pump. My engine always seems to stop in that position .....

[Rangy35]

Check the sediment filter/separator, when is the last time you cleaned it?

[Troll Hunter]

Thanks for the tips, guys. A split, but not totally failed, diaphragm could well explain the reduced power, but not total power loss. I'll strip the pump I removed last fall and see if I can fix it. I seem to remember seeing, some time ago, a repair procedure using a commercially available o'haul kit. Does anybody know if these kits are still available, and if so, from where?

Mike4444244, I can mount a gravity feed fuel supply, but to test it I'll need to be able to run at full power, probably up hill, so this will be a last resort test.

My engine must be the same as yours, CW, because the hand priming lever is always "limp" whenever I try it. I'll turn it over by hand and try priming with the engine in a different position.

Rangy35, what sedimenter? Since the 300Tdi is a replacement for the original, gas guzzling V8 lump, there is no sedimenter. Perhaps I should add one. Having said that, I carefully poured the diesel from the filter I removed yesterday into a clean jar, and there was no trace of water. Not even a little drop.

Since I'm off on a 4,000km round trip into northern BC on Easter Sunday, and I've no chance of getting a replacement pump by then, tomorrow I'll probably buy a 12V electric fuel pump that I can jury rig if necessary.

Thanks, again, for your help, and I'll update when I've found/fixed the problem.

Mike

[Daan]

could it be a split intake hose? lower turbo pressure would result in lower fuel delivery. Common problem, but can be hard to spot.

[mick110]

could it be a split intake hose? lower turbo pressure would result in lower fuel delivery. Common problem, but can be hard to spot.

Along the right lines there;more like internally delaminating turbo hose stopping full air flow ,rather than fuel......ie; it's being strangled.Also flush out /clean intercooler & fit new air filter.

Mick

[ballcock]

Having recently purchased a Disco 300tdi auto I have been disappointed with it, driving it back from Derby to S. Wales I found it rather sluggish accelerating. but when on the open road it will quite happily sit at 70-80 with no problem. trying to diagnose the fault I found the auto box to be slightly over filled and thought that could be the fault. Having read this thread I decided to investigate the lift pump. removing the pump I found that the washer on the shaft that pulls the diaphragm had come off the end and therefore the lever arm was not operating the pump. I don't know if this is a common failure on a Delphi pump and presume that when I replace it all will be well.

[dailysleaze]

I had a turbo hose split once. On hills that would normally go up in 4th at 40mph, i would need to keep changing down and it would get slower and slower. Eventually it would clamber over the top in second gear about 15mph

[Troll Hunter]

Update:

Thanks for the tips about split or de-laminated air hoses. Although I've suffered that once, it hadn't occurred to me as a possible cause for loss of power.

So, first check: I removed both the hose from the air filter to turbo, and the hose from the i/c outlet to the manifold. Both were in excellent condition, so the problem wasn't there, and they were both replaced. I also fitted a new air filter, just in case.

Second check: I jacked up the right hand front wheel, and with 5th gear engaged I turned the engine over by turning the wheel. With the fuel filter vent screw open, I tried the manual priming lever on the installed lift pump in all crankshaft positions, but it was never anything but "limp". No fuel came out of the filter vent, so no success at hand priming. I then ran the engine with the filter vent valve removed but no fuel was ejected. I concluded that the lift pump is still delivering fuel, 'cos the engine would still run, but insufficient to deliver full power.

Third check: I tried to repair the lift pump I removed last October, but it seems to be impossible because the upper and lower parts are joined by the edge of the upper part being rolled under the edge of the lower part, forming a sealed unit, probably with the edge of the diaphragm forming a gasket. I seem to remember that earlier lift pumps could be disassembled, because the two bowls were joined by 3 or 4 machine screws.

Conclusion: The lift pump is FUBAR, so get an electric fuel pump! This cost me about GBP25, and delivers up to 35 GPH at 5 - 7 psi. Installation took a few hours, mainly because of the difficulty of putting it somewhere where I didn't have to change the existing fuel lines that connect to the mechanical lift pump, since I want to return to this configuration when I can get a new pump. I ended up cutting the two hose connections from the lift pump I removed last October, so that I could use them to connect 5/16" vinyl hose to the original fuel lift pump suction and discharge lines, without needing to alter the original lines. The electric pump itself is now mounted immediately inside the radiator grille. Not ideal, according to the installation instructions, but it's just brought me 400+km, with a twelve foot trailer,, and full power has been available whenever required. It seems that the problem is solved.

Many thanks to you all, again, for your suggestions and help.

Mike

[mike4444244]

Glad you're mobile again! IIRC the FIP can pull some fuel through on its own, enough to just about run but not rev

Sadly the mechanical lift pumps seem to be a bit of a lottery when it comes to longevity!

Mike

[dailysleaze]

Have you got a link for the electric pump?

[Yostumpy]

if the lift pump was a delphi unit, don't they have a screw in the centre of the cap, undo this lift off the top, and clean out the guaze filter. If the sealed pump is blocked with gunge, I do hope you haven't got the dreaded 'diesel bug'

[ballcock]

I changed my lift pump today, as I said earlier my Delphi pump was not pumping as the diaphragm shaft was not connected to the lever arm. The pump I bought was from Bearmach as I have the luxury of being able to pop in there. Cost less than £25. although there is a great improvement, it is still not right. Possibly because I've probably messed up the fip settings. but it does prove that the engine will run reasonably well with no lift pump operating. The symptoms I was having was sluggish acceleration once it reached cruising speed it would maintain 70 on an open road with little problem.

[Troll Hunter]

You're absolutely right, Yostumpy, the Delphi pump does have a screw on top, but this only provides access to the inlet filter, not to the diaphragm. I cleaned a very few small pieces of debris from the filter, and there was no sign of the dreaded "diesel bug". The mesh was really clean.

I don't know if I have a link to the pump manufacturer, DS, since I am now well north of my home, and all the paperwork is in my w/shop. I got the pump from a local motor factor, and I doubt that it was locally made. Everything seems to come from China, but I'm sure that if you Google "12 volt diesel fuel pump", or put the same string into e-Bay, you'll get plenty of hits. I'll try to remember to look for a link when I get home, but that'll be a couple of weeks away.

Mike