Possible fuel pump seal problem

[tonymOz]

Hi guys
I have a 4m40 and there is a flat spot when accelerating through the gears. It seems as if there is fuel starvation and it mostly happens in 3rd. The engine hesitates for a second and then picks up again.
I've been checking the forums and I was wondering whether it could be the fuel pump seal.
I get about 13l / 100km and there is a bit of smoke under load - although not too significant.
Any ideas?
Thanks

[Dadeo]

Hi TonymOz
I reckon it is not a pump seal as this is usually indicated by ruff/difficult starting after being turned off for a period of time ie, overnight. Usually air will leak into the fuel pump and then start like a bag of poop while it purges the air out. Once it's running it's not an issue until it sits for a while again.

I don't pretend to know a great deal but I'd consider dirty injectors perhaps? I can imagine a hesitation between gear changes as you back off and then get on the throttle again. 13l/100 is a bit high, depends on what you're asking it to do but I get 10l/100 tooling around the burbs. A bit of smoke is pretty standard. May also be pump tuning? I'm sure there are others on the forum with more suggestions.

You may want to look at running the 2 stroke additive as well? Has many advantages and keeps it all nice 'n clean inside too.

Phil

[schnitzel]

is it a manual or an auto? if it is an auto and it happens between 1800 and 2200 rpm its your alternator.

[tonymOz]

Hi TonymOz


You may want to look at running the 2 stroke additive as well? Has many advantages and keeps it all nice 'n clean inside too.


Phil

Thanks Phil, I'll try the two stroke additive and see what happens. I did run some injector cleaner and found that it smoked more. I recently bought it so not sure when the injectors wee last done, 250k on the clock so they are probably overdue.
Do you have any more info on the two stroke additive, I've never tried I before.
Cheers

[tonymOz]

is it a manual or an auto? if it is an auto and it happens between 1800 and 2200 rpm its your alternator.

It's a manual, thanks schnitzel.

[Downunder35m]

So you have the same engine like my old rust bucket...
You might not have noticed yet, but having problems in only one gear is highly unlikely.
Just so you have something to look at:
Find a spot going uphill that changes from a left turn to a right turn and try to drive it with a max of 2200 revs.
If your engine goes flat and has trouble after the left turn and going into the right hand turn your fuel pump is not picking up correctly (the one in the tank!).
If you notice a lot of smoke when coming down from high revs quickly and also use a bit of engine oil it is most likely your filters in the rocker cover are blocked (quite common).
If you can keep a constant speed uphill at around 2500 revs but the engine dies quickly down around the 2000 revs (not too steep of a hill please) you are either starving of air (dirty filter, leak after the turbo) or your turbo needs a bit of tweaking.
If all the above is false and your problem only started recently I suggest to give the whole air and fuel system a good look and clean.
Last but not least you can try to tune the fuel pump and turbo, I posted some instructions for it and other members added more details to it.

I don't think it is a seal problem on the pump as you would have starting problems in the morning as well as problems on the freeway.

[chutsy33]

( If your engine goes flat and has trouble after the left turn and going into the right hand turn your fuel pump is not picking up correctly (the one in the tank!).

Do the 2.8Ts have a pump in the tank? I thought only the petrols had tank mounted fuel pumps.

[Downunder35m]

To be honest I never checked as it is pain to get there if you have drawers in, but even if there is no pump I know quite a few Pajeros develop this dead spot after cornering uphill.
So it might just be the pick up system for the fuel and no pump, result is the same.
But in my case this only happens if the tank is below one quarter full.

[nvmpaj]

There's no pump in the tank for the deisel . The injector pump does all the work . My 4m40 had the same trouble on hills , took it back to the dealer and they didn't want to know . I basically ignored it , but when I repaired my motor a few years back , I changed the pump , and no more hill problems . I'm guessing a deisel specialist could tell you if the injector pump is working correctly

[nvmpaj]

Just to add your filters may need work . The engine bay one , change it . The rear in tank one can be cleaned , lift the rear carpet , the inspection plate under that allows access to the pick up .

[Hunty]

I hated this problem had it for about a year. I got the pump rebuilt (wasn't happy with the people who did the job) still had the problem, replaced injectors. Tuned and tuned a few more times on the dyno. Cleaned the filter in the tank even tho it was clean. Had the pump tuned by someone else. Changed air filter. Bypassed the fuel line with hosing. The only thing that got rib of the problem was to put an in line 12v pump in the fuel line. So my thinking it was a fuel starvation in the supply. Is there a pick up in the pump? If so that could be you problem.

Here is the post I put up: http://www2.pajeroclub.com.au/forum/...siel+flat+spot

This drove me absolutely crazy! I really hope this helps!

Hunty

[schnitzel]

I hated this problem had it for about a year. I got the pump rebuilt (wasn't happy with the people who did the job) still had the problem, replaced injectors. Tuned and tuned a few more times on the dyno. Cleaned the filter in the tank even tho it was clean. Had the pump tuned by someone else. Changed air filter. Bypassed the fuel line with hosing. The only thing that got rib of the problem was to put an in line 12v pump in the fuel line. So my thinking it was a fuel starvation in the supply. Is there a pick up in the pump? If so that could be you problem.

Here is the post I put up: http://www2.pajeroclub.com.au/forum/...siel+flat+spot

This drove me absolutely crazy! I really hope this helps!



Hunty

Be very careful with this dodgy brothers fix, putting an inline electric pump is known to force diesel past the front seal of the injector pump, this diesel then enters the sump and dilutes the oil to a point where the engine can then run on the sump oil, an effect known as diesel run on. The motor then revs uncontrollably until it explodes. A lot of car yards use this cheap fix to hide dodgy injector pumps as you can get away with it for a while but it will eventually catch up with you.

[Hunty]

Righto so how do we diagnose this problem or what would cause it? Wasn't happy that I had to put the electronic pump on but was just happy to have the problem solved after trying so much. So Schnitzel what would cause the pump not to suck enough diesel so it doesn't have the flat spot. I've also put a new long range tank on with a new fuel sender. Sorry for high jacking TonymOz I really want to get my faith back in the old girl.