Help please misfiring M35 multifuel. - Steel Soldiers::Military Vehicles Supersite

martin · 07-26-2009, 17:37

Hi
We have just attended the War and Peace show in the UK.
On the way home the truck was badly missing intermittently and lacking power.It also stalled at tickover a few times. It would then surge for a while and then slow down again.
The previous owner had problems with the in tank pump but replaced it. Everything was OK the last time we went out (250 mile round trip). He also put on a small filter instead of the primary one which he disconnected. I fitted a larger one but I suspect this is the cause of the trouble as I am sure that it's fuel starvation. I am going to replace the original primary filter (and the others) but could not find an element as the centre diameter of mine is 33mm and the ones I saw at the show had a smaller hole which did not match up with the perforated plate that sits on top. Please can anyone confirm my diagnosis (or not!)
Thanks,
Martin

dabtl · 07-26-2009, 17:48

Get the jatonka primary spin on adapter and forget the problem.

WillWagner · 07-26-2009, 17:48

To confirm your diagnosis, ya kinda gotta be there and be "hands on".
The fuel system would be the first place i'd start, sounds like you are on the right track. If you suspect the aftermarket primary, you could bypass it and see how it runs, bet, if there is junk in your tank, removing the primary will allow the junk to find it's way into the fuel system...remember, the flow goes from the tank, thruoght the primary, to the low pressure pump, through the secondary fliters and then to the IP ad out to the injectors. The only true way to find the issue it to put some gauges on it and see what the pressures are. A day or so ago, there was a guy here that had stalling issues and it looks like his issue was/is the check valve in the pumping head. Keep us posted, we all learn from the problems that happen to others and the fix they find. Good luck.

Divemaster920 · 07-26-2009, 17:55

If when you change the secondary filters, you do not have the right gaskets and your old ones are bad....take the ones that come with the new filters and put them on a belt sander and remove some of the outside material. That will allow them to go into the slot and seal.
Good Luck.

martin · 07-26-2009, 18:44

Thanks guys.Will let you know once I have sorted it.

cranetruck · 07-26-2009, 19:09

Sample the fuel from the tank to make sure there is no water present. Water settles to the bottom, so open the drain plug for this.
The primary fuel filter is also a water separator, so it serves an important function. The micron rating of the filter should be 40.
If the fuel is not the problem, check the timing.

martin · 07-29-2009, 11:45

Hi
Just dropped the filters.
Primary had some water, first secondary was half full of muck and second not a lot better.
Will clean tank and then flush and renew.
I think this predates me as I filter and water trap all my fuel before it goes in.
Thanks for the help guys.
M

martin · 08-26-2009, 12:49

Hi
I removed the tank and cleaned it out although it was pretty clean.The pump looks like new. There were 2 pieces of metal lying in the bottom of the tank.They looked as if they fitted on the bottom of the pump but they did not fit it! Egg shaped with a cut out in the middle that curved around (I know a pic would be great but technical daughter is away!).
The 'wrong' primary filter is still in place until I can get some pipe to refit the original.
I changed the 2 secondary filters.
The truck started after we bled the system.There are a few bubbles in the clear return pipe running along the injectors.
Ticks over OK but sometimes the exhaust flap bounces so I suspect a minor missfire still.
Will rev up to about 2100 then will missfire a lot worse.
I put in mostly pump diesel so fuel should be OK.
I still suspect fuel starvation due to the small primary filter but are there any other areas to look at? Even before current problem the engine was not a willing revver.
Thanks,
M

Stretch44875 · 08-26-2009, 14:34

The plates could be from a previous pump, they are known to fall off. I think the ones you see are the shim plates that go around the impeller.

See what happens when you get the original filter in place.

martin · 08-26-2009, 20:13

I tried revving the truck and with no load the missfire is at the same revs so I wondered if there was a governor or rev limiter as I would have thought fuel starvation would only be an issue under load.
M