Oil & Fuel Engine's speed-range suddenly changed... Foton 254 with KM385BT engine

[SensibleNick]

Hi all.

I have a Foton/Europard 254 that has just done something a bit odd.

While driving with the engine at about 2500rpm, the revs suddenly dropped to around 1800(?) and wouldn't go any faster. I Limped home, expecting a slipped control cable. I hadn't been pressing hard on the acellerator pedal - I had held it at a comfy RPM, and without moving my foot the RPMs dropped to a lower rate. It sounded as though I'd just lifted my foot.

I also noticed the the idle was also out - much lower than usual, and near to stalling.

The cable hadn't slipped. The control lever is still causing the limiting rocker on the control shaft to move up against its stop-screws. After thinking "fuel starvation" I checked the filters. Nothing odd there. They seem fine with plenty of through-flow.

So I'm scratching my head and asking ... is there some component within the injector pump that may have slipped or broken? Everything works as it should... just with the max and min RPM lower than they used to be.

Useful Info?

• The injector Pump is a 3i344 - or at least - has an identical layout to one.
• It doesn't lack power at the RPM range I have available. It really doesn't feel like a fuel starvation problem.
• Adjusting the stop-screw for max RPM does allow me to get it back up to 2200 rpm, but I run out of adjustment. I have adjusted the lower RPM stop so that it idles happily now.
• I had recently discovered that the pump's oil level was low. Not dry... but really low. So I topped that up. All seemed fine.
• I have recently overhauled the sight-glass under the fuel tank and its mesh filters. They had become massively clogged. The main (canister) fuel filter has about 100 hours on it, and appears to have fantastic through-flow.
• I have checked the cotter-pin that holds the limiting "rocker" on the displacement-control shaft. ... it's fine.

All suggestions are welcome - I'm really scratching my head here!

 

[SensibleNick]

Following a suggestion from someone who PM’d me, (thanks - you know who you are) I had a look at the governor.

It didn’t seem stuck - but I found the cause.

The spring that pushes the bearing forwards has a leg missing. It was thankfully jammed in the bottom of the housing and hadn’t been munched by the governor.

Does anyone have a dead pump that can be plundered for a spare?

Or does anyone now the part number for this?

 

[AWSubie]

From the picture this looks like a pretty simple spring. If it is hard to find online, I would make one from scratch. For help with the making of a spring go to YouTube channel “this old tony” and search for “making springs at home”.

 

[Bob Rooks]

It's a good thing these engines never run away.

 

[SensibleNick]

From the picture this looks like a pretty simple spring. If it is hard to find online, I would make one from scratch. For help with the making of a spring go to YouTube channel “this old tony” and search for “making springs at home”.

It looks as though I owe you a pint mate.

I’ll update when I’m done, but this is the last 5 minute’s work and first attempt....

 

[thepumpguysc]

WOW.. great job of finding & fixing the problem.!!

 

[SensibleNick]

So. We’re up and running again with correct throttle response.

Thanks to all who helped!!

Piano wire was sourced at the local hobby shop. I got three meters (anticipating a long learning curve) and only used one meter.

The mandrel diameter was calculated using this online resource. Helical Spring Mandrel Design Calculator

I didn’t use a wire-tension system to wind on the mandrel - just a chunk of bronze up against the mandrel itself. (See picture)

Total cost - about $5 including new gasket material to re-seal the pump.

 

[thepumpguysc]

I just cant get over how impressive that fix is.!!!

 

[Bob Rooks]

Great job! You make it look as easy as writing down the part number.