Fuel starvation??

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J

jonnyt

Active Member
Posts
213
Bit of an odd problem.

300tdi, 1998 on an R plate. Took it for a long run today (200 miles).

Going up a hill after about 50 miles it started getting a bit sluggish and slowly lost power (2 mins or so). I'd been on a motorway for about 30 miles I suppose and was in a bit of a rush, doing about 70 I guess. Accelerator did nothing. Checked everything I could. Nothing obvious - oil ok, no water in it etc.

Tried to start it again, cranked a few times and it started. With a little feathering of the throttle it was fine so off I went. It then happened again in the same way, up hill again.

Then thought might be over fuelling so drove very carefully to ensure no over fuelling and stayed below 60. Happened again. and then finally a fourth time. I stopped before the engine died completely on the last occassion and feathering the throttle kept it going, but it wouldn't recover properly. Then stopped it and it started fine and got me home. When its running its perfect, smooth and no loss of power.

I also checked the fuel filter and that was full with fuel.

Only work done on it recently is a change to the cambelt but can't see that it would be related.

It seemed to me fuel related (when it starts its a bit like when you've just changed a fuel filter), but don't see why it would be so intermittent.

Any ideas?

Thanks guys.

Jon
 
check the fuel sedimentor housing for pinholes.
theres a crud trap on the outside between boltholes and it rots thru the ally housing.
empty sedimentor and give the housing a good poke in good light.
if it is this, your next thread will be how to get the fuel unions out!
 
Thanks for that. Wrong guess on next post though - where's the sedimenter??:)

I assume that the suggestion is that the sedimenter allows fuel to leak out causing a air to be dragged through the lines. It then fills up again when it rests?
 
wont get a leak from it as the pump sucks from it. when at rest the hole allows air back in so fuel drains back to tank.
there might be a darker area round it where fuel capillaries into the accumulated **** that sticks to the chassis. bit hard to tell in this weather when its all wet to start with.

oh, sedimentors located underneath, on the inboard side of chassis rail, off side of disco, level with front of offside rear wheel. kind of looks like a fuel filter without a cartridge.
11mm spanner on bolt on top of housing, bottom drops off. dont bother with the drain screw, it'll shear off.
put a carrier bag over it when removing to prevent diesel going up yer arm.
check seal when replacing.
dont forget to poke the inside of housing for pinholes.
keep us posted.
 
Thanks - I will do. Looks like it's not going to be this weekend though sadly.

I take it from the earlier comments that the straightforward removal indicated by your instructions might be a little more tricky than you suggest!!!!
 
removal of sedimentor bowl should be reletively ok, if you discover holes in the housing, it gets a bit tricky due to seized components.
it has been known to cut the unions off and sleeve the input and output with some decent fitting tube, doing away with the sedimentor completely.
also dependant on how handy you are with the spanners.
 
Last edited:
Had a look yesterday.

As far as I can tell I don't have a fuel sedimenter - I've traced the fuel lines from the tank to the pump and there is nothing between the two.

There are no leaks anywhere that might suggest a leak of fuel / air being drawn into the system.

However, what I did do was unscrew the fuel filter and as it should diesel leaked from the top. I hadn't thought about it but it didn't do this when I took it off at the road side.

The only other thought I had (other than perhaps lift pump failure) was that the breather in the fuel cap may have been frozen up causing a partial vacuum in the tank restricting fuel flow as it was during the very cold weather last week. Could it be this?

Thanks,

Jon
 
Just a thought check the fuel lines coming from the fuel pump I had a similar problem where one of the lines was chaffing on the chassis. At the top of the tank there was a pin hole in one of the lines which was allowing air into the fuel. It caused loss of power like you described and the engine kept wanting to stall.
 
probly wont see fuel coming out as its a vacuum, not pressurised.
you could try a transparent tube in line with the lift pump and filter and watch for bubbles.
other methods involve pressurising the fuel line from the tank and try to blow fuel from the leaky bit. bit involved and sometimes still difficult to spot.
what have you got where the sedimentor should be? has it already been removed?
 
I don't think there is anything where the sedimenter was. As far as I can tell it wasn't fitted to all vehicles. I know it hasn't been removed because my father owned it from new before I bought it.

Re fuel lines - I see that it is a vacuum but wouldn't there be a trace when the vehicle is resting and the vacuum isn't there?

Do you think the frozen fuel cap is totally impossible as a possible solution. I have to drive a fair way over the next week and would like to get this sorted.

Thanks for all the help,

Jon
 
the trace you'd get is a damp spot where the fuel dribbles back under gravity, so dont think you'd get an obvious drip.
the frozen fuel cap would be more apparent with a full tank, as a vacuum would develop quicker. try removing the cap next time it does it, but i doubt its your problem.

go for the trannsparent fuel line and look for the bubbles when its running, or remove the inlet to the filter and put the end into a decent size jam jar / coffee jar and operate the primer. look for bubbles rising up from the fuel in the jar. if its bubble free, the problems elsewhere.
 
I had the same problem with my 300tdi r reg 90.
It would be alright if i left it running, but once i got going over 30 it would lose power and grind to a hault, or a crawl.
i replaced the fuel filter as i had let the fuel run a bit low and came to the conclusion that junk from the tank had blocked the filter.
new filter £5 on ebay, 20 seconds to fit, problem solved !
at 1st inspection of the filter it seemed alright, but the new one did the trick !
hope this helps !
 
I changed the filter when I did the cam belt not so long ago. I will replace it again just in case there is a problem with the filter.

Interesting about the comment of the full tank - filled it up today and its been an absolute nightmare (it has been miserable here too in terms of weather). It stopped about 6 times in the course of a journey, same symptoms again. Bizarrely though I've just taken it out again and its absolutely fine.

The odd thing is the intermittency of it - if it was a hole in a fuel line as said wouldn't it be a constant problem?

Its almost as if something is freezing with flow of fuel and then as soon as it stops it thaws and its all fine again.

Really bugging me now!! All thoughts, however ridiculous welcomed.

Thanks for the help guys,

Jon
 
Jon-if you loosen the filter bleed screw,when it is ticking over,what comes out?It should be clear fuel dribbling,any sign of bubbles and you have air ingress somewhere-mine suffered from air ingress on the short rubber pipe to the lift pump supply-also check the pipe that feeds from the filter manifold to the injector pump,at the injector pump end the pipe was slightly loose (seems like the metal pipe shrinks away from the rigid nylon in this cold weather-I put a smear of sealant round this)The only real way to check is to undo the leak off return pipe from the injector pump and put a piece of tube on instead into a container,run engine and observe what is coming out of this pipe,it needs to be clear bubble free fuel-any air and you have to find where it is getting in
 
Chatting to somebody last night, they suggested that it sounded like frozen fuel in the injectors - when you stop the engine temp warms up the fuel and it starts again. Sound a possibility? I don't know whether Tesco fuel has the additives at this time of year.
 
Don't know where you are but pump diesel is only good to -15c-if you are seeing night temps below this, add 5-10% unleaded to the tank-normally if the fuel is waxing,car starts and then dies in first 100 yds-once they get going normally keep running.
 
biolandy said:
The only real way to check is to undo the leak off return pipe from the injector pump and put a piece of tube on instead into a container,run engine and observe what is coming out of this pipe,it needs to be clear bubble free fuel-any air and you have to find where it is getting in
Click to expand...

even better, and probably easier and get the visuals under engine running conditions.

jonnyt said:
Chatting to somebody last night, they suggested that it sounded like frozen fuel in the injectors - when you stop the engine temp warms up the fuel and it starts again. Sound a possibility? I don't know whether Tesco fuel has the additives at this time of year.
Click to expand...

understand this if its first thing in morning, but once running should be ok.

forgot if its arleady been mentioned, but is it only in the cold weather the problem occurs?
when did you do the timing belt in relation to the problem?
 
Timing belt was done probably 500 miles before the problem started so I had pretty much ruled that out.

It was awful this morning - only got about 200 yds from home before it cut out. Still no visual issues. I'm going to have to get underneath it soon - not that attractive at the moment!!
 
Just had the same problem on my 300tdi.

Checked the sedimenter and the fuel filter, still wouldn't accelerate above about 2500 revs.

Running out of ideas, it was freezing working outside, and fearing an injector pump problem I asked my local diesel people to check it out.

Thery ran a pipe direct from the tank, by-passing the fuel filter and lift pump, and it was fine.

So I replace the filter with a good quality one, £6, and the lift pump, £13, and all is fine.

If time is critical buy both, change the filter first and if that works you have a spare lift pump.

Best of luck.
 
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