Hello all, I thought I'd post this here, as I've found these forums very useful in the past and thought others may find this helpful.

I own a 2004 Jeep cherokee 2.8crd. About a year ago it started intermittently cutting out and coasting to a stop. After this happened a few times a pattern emerged- it typically happened at about 50mph and usually within a few seconds of applying close to full throttle.

From this forum, I read about all the cases of air in the fuel and clogged fuel filters. So I replaced the filter and checked the fuel flow by running a transparent pipe section between the filter outflow and pump inlet. I made it long enough to loop up to the window so I could see it as I drove. There was no air, and it eventually cut out again with the new filter.

I was at a bit of a loss, so took it to my local diesel garage. They checked what they could and told me the engine was shutting off because the ECU believed the Fuel rail pressure was too low. Their suggestion was to replace the rail pressure sensor, then the pressure control solenoids, the high pressure fuel pump etc until the fault was gone. As it was an intermittent fault, this would take a long time, and would cost more than the car was worth.

This left me a bit deflated. But I thought I'd see if I could find another solution. I realised that, if I never pressed the throttle more than 1/4 it never cut out. I confirmed this in about 1000 miles of mixed driving. This made me think it was a fuel flow problem rather than an intermittent electrical fault. The car was fine when fuel demand was low, but couldn't meet the physical inflow demand at 50mph and wide open throttle (I think this may be the highest fuel demand case in normal driving- rpm is high and load (air resistance) is high).

That made me think that the fuel supply system was marginal on my machine. After reading about lift pumps on this forum, I though I'd fit one as it would surely help increase flow regardless of the reason for it being just a bit too low at maximum demand.

I found an in tank pump (an aerotech I think), ordered it and got ready to fit it. Once I'd dropped out the fuel tank, it quickly became apparent the design was different to the ones pictured on the guide to fitting a lift pump on this forum. My Liberty KJ is a British registered car and is branded a Cherokee. The tank, while a very similar shape, had a different system for connecting up the fuel hoses- the breather also attached to the yellow insert, and not the tank directly. When I removed the yellow insert, I also noticed it wasn't quite the same size as the replacement aerotech pump (about less in diameter) and the system for suspending the fuel pick up was different- in my tank it was clipped to the bottom of the tank on two moulded in rails.

While looking at all this, I found a very course filter in the in tank pick up anti-surge box clipped to the bottom. This was a plastic net about 100mm by 40mm. It lived inside the anti surge box. Interestingly, I also found a large globule of very thick grease like stuff covering about 10% of the area of this filter. I have no idea what it was or how it got in there- it didn't look like built up dirt, it looked completely homogeneous and as if it had been added in one go. I removed it and put everything back together as it was (I didn't fit the lift pump). Since then, I've done over 500 miles with no failures at all and suspect it is fixed (I'll post again on this thread if it happens again). I would have expected it to fail three or four times in this distance.

I'm still surprised this has fixed it (if it has) it only covered 10% of this filter. It makes me suspect that the fuel system on the crd has very little 'spare' capacity.

If anyone is interested, I can add pictures of the fuel pickup system and the offending globule of gunk!

Bill

Bill, thanks for the post. I would be particularly interested in that possibly offending globule - can always learn. Yours is a different year model to mine but I'm surprised there aren't more takers of your kind offer of photos. Thank you.

The excuse I've been waiting for!

Different to US tank connections (note the breather):



In tank unit- oblong bit is the surge tank, about the size of a (UK) house brick. It also had the fuel sender attached. The long black pipes link it to the round top of tank connector.


Globule in situ in the in tank fuel surge tank. I've already removed the bag that was connected to the outflow. The globule is a bit more fragmented than it was originally as I'd already been fiddling with it:


Apologies for the quality of my photography.....

Looks like ectoplasm
Maybe that's why you have ghosties in the machine.

Just a reminder that diesel fuel is or can be an excellent growth medium for algae which might tend to catch on that screen and eventually seem like a greasy glob.

_________________
Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

I agree with papaindigo. Thanks for the photos Bill.
Do you treat your fuel with an algicide?
I could be making an incorrect assumption if you have been and but this is still a trap for many young players.

I do every 2nd tank in our mild winters and when its humid every tank. That looks awfully like algal growth which could be averted - but on the good side of things it appears the tank pre-filter has done its job. Some will argue this is not necessary. It is.
Some people think you can avoid ingress of water vapour into diesel tanks. This is utterly impossible and the stuff loves to grow in the anaerobic conditions at the bottom of a diesel tank.
There are practices like not filling up after the ground tanks have been filled but that won't stop it all. The vapour entering the tank under cool conditions will also build over time and given the imiscibility (dislike for one another) & differing densities settle to the bottom.
Given the age of your vehicle and the number of tanks that could've passed through that and the water that could have entered no matter what care you had taken - this is a distinct possibility.

If you do treat with an algicide after not having done so for many years - plan on a fuel filter change.

I've never used an algaecide and didn't even know it existed until now, so that may have been the issue. The failure mode caused by it is quite interesting though. I replaced the filter as part of the initial attempt to fix it, so hopefully I will be OK for the foreseeable future.

Hello again. More information on this for anyone interested.

After a year and a half of trouble free motoring these symptoms returned. So I removed the tank again and found a much smaller blob of debris. I cleaned it out, and, although things improved a bit, I could still make it cut out on full throttle at 50 mph. If I stayed below 50% throttle in this speed range, all was fine.

So I thought I'd investigate further. I added an electric lift pump. This made a small difference- the number of times it cut out reduced by about 50%, but I could still make it happen relatively easily. I removed the lift pump to double blind check, and the symptoms returned to exactly where they were.

I replaced the fuel filter. No change.

I then rigged up an intermediate fuel tank post filter pre pump (actually a glass bottle in the cab) to see what was going on. It was soon clear this remained full even when it cut out. So I knew the fuel supply to the pump was not an issue.

At this point I strongly suspected the problem was simply that the fuel system was unable to supply enough fuel to the cylinders at high pressure under the maximum fuel demand condition. This was the only thing I could think of that would show such symptoms. And it had to be a different reason to last time. This made me think it was either the fuel pump, the end of fuel rail pressure regulating solenoid or the injectors flowing or discarding too much fuel.

Sadly, investigating these is all beyond my competence. So I decided to get a professional involved. After a bit of googling, I took it to a local Jeep expert- Chris at Surrey off road. He was superb, and very quickly spotted that a small amount of fuel was pooling around the injectors on the outside of the head. This only happened after a hard run, and wasn't visible at idle. He removed all four injectors and sent them to be tested. This revealed that two were cracked and leaked externally at high pressure. Chris replaced the two injectors with refurbished ones and this has cured the problem completely. I have tested it extensively for the last two months, and have had not a single re-occurrence.

Bill

Thank you Bill for sharing your experience with injectors , I'm one of lucky ones on this side of the planet i had to replace two injectors in my jeep aswell, thanks again.