300tdi lacking power - fuel pump?

Hi,
Spent the last few days (when work/weather permitted) trying to track down why my 1998 130 defender 300tdi has lost power.
Apologies for the longish post, I thought it best to detail what I have done/seen so far.

Symptoms : Normal idle, loses power over ~50kph or up slopes. No black smoke. Turbo seems to spin up normally. The issue could be temperature related (currently swinging either side of freezing)

I stared by checking the filter (clean, no water, but not replaced yet..). Also checked I was getting fuel out of the air bleed. Seems fine, which I assumed meant my LP fuel lift pump was ok? Maybe this is not a perfect test, I know these pumps are known to fail.

After this work I took it out for a spin, and it all seemed fine, usual power and revs. However the testing day was (just) above freezing, and the original issue was on a colder day (-5c).
The next day the temperature dropped, and the problem was back. Not sure if this is a coincidence.

Yesterday I removed the sedimenter (some crud, but no water) and drained some fuel from the tank (clean, no water, got covered in fuel as is traditional). My theory was that the issue I had was water somewhere in the system freezing up and causing a partial blockage, but I’m not seeing any evidence of this.

Today (around freezing) I tested it again, but it is very gutless, so had to limp home. Not smoking, so I’m assuming fuel starvation rather than airflow, but tried removing the air filter just in case it was frozen up. Sadly no change.

The engine idles normally, but when revved up in neutral it runs a bit unevenly at higher revs and doesn’t seem to rev freely. After this it idles poorly for perhaps 30s, which I’m assuming is due to a fuel shortage.

Next plans are to try and connect a temporary gravity fuel feed into the filter, assuming I can get the banjo off with a heat gun or boiling water.
If this helps I might remove the sedimenter again and try and blow the feed line through in case it has got clogged.

From reading the forums, I should probably check the vacuum line from the air intake to the turbo is connected and not leaking. Possibly also check the diaphram(?) in the HP fuel pump is providing boost.

At this point any words of wisdom, or just pointing out the blindingly obvious I have missed gratefully received.

Regard from a snowy Iceland

You have listed most checks to try, Gravity to filter and it then works suggests lift pump and/or feed issues.
Other checks are air intake pipe, air filter and pipe from filter to turbo are not collapsing internal and blocking.

The small pipe from the turbocharger to the injection pump, nylon 6mm od.
Or the diaphragm inside the injection pump under the four top screws.

It does sound fuel related (as in not enough). My 300tdi suffered similarly (though not quite as bad) and was cured by getting the FiP serviced.
The vacuum feed to the pump, in conjunction with the diaphragm open the fuel valve inside the pump allowing more fuel to pass.
A blockage in the pipe or a split/leak in the diaphragm will cause these issues.

Thulelandy said:

Next plans are to try and connect a temporary gravity fuel feed into the filter, assuming I can get the banjo off with a heat gun or boiling water.

Click to expand...

try doing this but a several different points of the fuel systeminto the pump, into the filter, and into the lift pump. If it is normal with these then you know it is a pickup/fuel pipe issue in the tak, if it runs at the filter but not the lift pump it is the lift pump that has given up the ghost. if none make a difference then the injector pump is the likely culprit.

Hi again,
Sorry for the delayed reply. Got held up by weather, work and a volcanic eruption, all the usual stuff.

Many thanks for the wise words. I finally managed to attach a gravity few fuel tank, which didn’t change anything. At the same time I could see that the lift pump on the engine seems to be ok, as I left it connected to the main tank and diverted the output into my gravity tank.

I have just removed the air line from the turbo output to the FIP, and this is not blocked. The membrane above the FIP seems intact, although I’m not sure if I am getting a positive pressure from the turbo. I can hear it spin up, but I need to try and improvise a manometer/pressure gauge to check. Tried removing the bolt over the membrane and pushing it down manually while increasing the rpm, but not convinced there was a difference.

I also noticed when removing the membrane and conical pin (and stupidly forgetting to mark the original rotation..) that the rider pin that contacts the cone may not be sliding smoothly in and out.

Not sure I have the time/weather to strip the top of the pump to get to the fuel comp mechanism. It may be getting to the point where I need to take the pump off and get an expert to convert large sums of money into a serviced pump.

I have also read that the input pipes to the turbo can collapse at higher revs, but I’m not sure if there is a soft section on the pipes between the air filter (currently removed) and the turbo?

Anyway, thanks again for the help, hopefully I’ll get more time to get covered in cold diesel again soon . At least most of the snow has melted now we are getting positive temps some of the time.

If you look at the tapered part of the pin you removed, you will see a more defined groove, this is its normal running position.

Whack a gauge in the 6mm boost line and see what boost if any you are getting.

Very much doubt you have a fip issue.

boost needs a load to come up to the 1 bar you should be getting

i have a permanent boost gauge fitted and if I take the revs to 3000 while at standstill i won't even see .3 of a bar but under max acceleration will see 1 bar at 2500

it does sound like air is leaving the system without permission

the rubber boost pipes do perish with time but you should be able to find the leak as oil will be present

that bottom boost pipe connector to the intercooler can be a bugger

lynall said:

If you look at the tapered part of the pin you removed, you will see a more defined groove, this is its normal running position.

Whack a gauge in the 6mm boost line and see what boost if any you are getting.

Very much doubt you have a fip issue.

Click to expand...

Hi Lynall, I may have to get creative with tyre pressure gauges and improvise a boost indicator. Or order one and wait a bit.
I very happily to hear you think the FIP is ok. I gather they are pretty reliable. Just read a post on another landy forum where someone optimistically tore their FIP down before checking other options. Didn’t end well. Not got down to the bottom of the intercooler yet to check the plumbing.

D1Nut said:

boost needs a load to come up to the 1 bar you should be getting

i have a permanent boost gauge fitted and if I take the revs to 3000 while at standstill i won't even see .3 of a bar but under max acceleration will see 1 bar at 2500

it does sound like air is leaving the system without permission

the rubber boost pipes do perish with time but you should be able to find the leak as oil will be present

that bottom boost pipe connector to the intercooler can be a bugger

Click to expand...

Hi D1nut, good to have some boost level values to look for. Air escaping without permission is likely. Much of life with my well-loved landy is based on negotiation and compromise rather than a clear hierarchy of command.
As I just mentioned to Lynall, might have to get creative unless I can find a suitable gauge over the weekend. Got some at work, but they are all for several 100 bar.
Your comment on being able to detect the leak due to the presence of oil made me laugh. Like most classic British engineering my landy seems to operate on the principle that everything being covered in a film of oil just means I haven’t run out of oil.
Not sure I’ll spot a new leak, but worth a go. Cleaning the engine is challenging right now as it is outside in the freezing temps, so the existing oily ‘patina’ is like tar.
Probably time to treat myself to a set of those nice colourful silicone pipes in my next spares order, and perhaps a fuel pump and several other bits just in case.

Not managed to find a boost gauge yet, but while reassembling the boost pin assembly (many thanks for comments pointing out I could use the wear line on the pin as a reference) I thought I’d try running with the pin/membrane removed as a test. What I was expecting was the FIP to over inject fuel as I reved up, leading to smooth but smoky running. This was just a quick static test.

As the wise amongst you (and now I..) know, this allows the pin following the boost cone to come quite a long way out on higher throttle levels, which made me panic it was stuck all the way out at max extent until I managed to coax it back in. So lesson learnt..

However, what surprised me was that I still see the same issue with low power/max rev limit as I wind the throttle up (by hand directly on the pump). It will rev up to a point, then start to run unevenly. When I go back to idle it continues to run unevenly for a short while (10-30 secs), or sometimes dies altogether.

This feels like fuel starvation, and makes me think I need to go back and check my assumptions on the fuel feed being ok. While I have seen the fuel lift pump seems to be pumping several ml/s, it may be failing at higher revs. I have also realised that I have yet to thoroughly inspect the fuel feed from the filter into the FIP. I’ll feel pretty stupid/happy if this issue is there.

certainly not an expert on the injector pump -but have spent an unhealthy amount of hours reading up etc.

from what I understand the pump wants to run at maximum fuel delivery at all times

the pin you speak of is actually an inhibitor to stop that section of the pump from doing what it wants to do - ie delver max fuel

so the hesitation to return to normal tells me that the pumps internals are dirty or sticky

but an overriding experience of mine is that the problem is simple and inexpensive to fix other than the time taken to find the actual problem

another bit of experience is that we need to measure stuff

so in your case a 21 euro mechanical boost gauge and some plastic pipe might be money well spent or a loss of i think 2 cups of starbucks

a long post with not much facts added

Well.. Finally got a chance to cover myself in diesel again, but this time with some positive results.

After a careful inspection of the plumbing from the fuel filter to the FIP, I found tiny bit of plastic in the fuel line, and I’m pretty sure this was the root of my problems. No idea how this got there, but I think it was partly blocking the inlet to the banjo bolt on the FIP inlet. When I blew the lines through I didn’t spot it, as it was cunningly acting as a one way valve. I only found it when I removed both end fittings and blew it through again.

Just took it for a quick drive up some local hills and it is back to its (semi)spritely self. I think I may need to re-adjust the boost cone, as it is blowing a bit more black smoke on acceleration than before, and it is making a great howling noise with the filter removed (back in now before I suck anything into the turbo), but v happy to have it back in operation. I will also treat myself to a boost gauge, and possibly a fuel pressure gauge as I’m still not convinced the lift pump is 100%.

Of course there are still several pages of slightly lower priority jobs I really need to do, but most can wait until it is slightly nicer weather outside. I have also just discovered that a front brake caliper is cracked on my kids Nissan D22, so that is next in line for a fix. Many thanks for the support with this quest.