'88 W124 250TD RHD NA.

Started to become really gutless - took forever to get up to any speed.

Suspected fuel starvation, so checked tank gauze - clean.

Changed air and fuel filters.

Removed lift pump and replaced O-rings.

Fuel runs fine from tank (I have a face-full to prove it!)

It starts fine, and idles fine. Press the pedal and it won't climb above 1200 rpm. Eventually it'll rise slowly to 4k. Try driving it and it will just about move off. Keep the revs up when changing gear and 25mph is possible, but that's max.

Having eliminated all other fuel-related points I suspect the injector pump, but I'm at the limit of my mechanical experience.

Side issues are that it's due an MoT (car safety check in the UK) in six weeks, which it will fail probably on rust on sills, perhaps more. If it's just welding then I'd look at having that done, but throwing money on having the IP rebuilt right now is not an option, as I could be faced with scrapping it in a few weeks if the welding bill is too high.

Right now it's on its way to car heaven, unless anyone's been here before and can point me to a DIY solution.

Thanks in advance.

Does it help to drive without the fuel filler cap?

Does it have anything of a catalyst or something that can clog the exhaust system?

Does it help to restrict the return line to the fuel tank?

Sixto
87 300D

I have its brother (see sig below)
It probably has a cat converter in the exhaust 1/2 way back. It maybe blocked. There is a flange on the exhaust just before it, try unbolting it & see if the problem is still there, it will be noisy while disconnected.
It also may have a problem with the fuel pressure regulator (banjo bolt)
Did this just suddenly happen or did it develop slowly over time?
Its unlikely it need a IP rebuild, at worst just a very minor repair.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

LOOOOOOOOONG Post:

Fuel pressure relief valve adjustment

Basically it's a "Banjo Bolt" (with a Spring pressurizing a Ball Bearing) that
regulates the Fuel Pressure (Provided by the "Lift Pump" on the side of the
Injection Pump) inside the Injection Pump.

If the Spring is WEAK it allows fuel to Bleed Off into the return system,
starving the I.P. of fuel.

So Sorry about the MOT.Yeah,If the bottom outer rails of the Chassis are
"Rotten" it'll COST to make it Good.

In Georgia (The U.S. State,Not the Cyrillic Country) RUST never stops
anybody...It's Effing Crazy,we used to have Required Automobile Inspections.

__________________
'84 300SD sold
124.128

Hi
sills shouldn't cost much more than £40-50. Might be cheaper to 'delete' them rather than repair the jack point - I personally will never use the standard Merc jack again....
Do fill the cavity with wax after the repair too!

cheers

__________________
cheers!!

OK, that sounds like one worth checking. Here's my IP:



On the reverse (engine side) of the IP there is a 17mm banjo - the pipe leads up to the return line, but there's no spring inside it? All help much appreciated.

Seems this is on the reverse of the IP, on the block side.

I have removed it, but how to access the spring?

The banjo bolt is not normally repairable.

Can you fill us in with some more details please.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

This is a UK model 1988, and I'm sure there's no emissions control kit.

Has got much worse over the last two weeks. I've run it on waste veg oil when possible, but I don't think that is the issue. Same results on 100% dino diesel.

you'll get better help on this forum. wvo unless REALLY treated well, can damage the IP and prevent power/compression. changing back to diesel does not help the issue.
try pinching off the fuel return line like Layback40 suggested, and also try driving with the fuel cap off. and tell us if anything changes.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Mine is a 87 UK model, private import to Australia. It has a cat converter.
You may have bad/blocked injectors from the WVO use.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

http://www.vegetableoildiesel.co.uk/forum/viewthread.php?tid=24659&page=2

I will put this up just in case he forgets to pop back and post the cure

another benz ruined with WVO.....

__________________
1995 E300 diesel

My suburban experienced a similar problem, turns out the excess fuel return check valve was stuck closed. not sure of the 603 has a check valve on the excess fuel, but maybe something similar with the fuel bypass.

__________________
Closing the store
Benzbonz.biz on your smart phone or tablet.

Excerpt from Simons post on the Uk vegetableoildiesel forum.

Then it dawned on me - the throttle cable was slipping through the non-standard clip that was in use. Took out the clip, replaced it with a clothes peg, and hey presto, lots of fuel reaches the engine. Just took it for a spin and was up to the limit at a rate of knots


This was the cause of all the grief lol, the throttle cable