12mm pump probs

[dturbopeck]

Right built a 12mm pump and stuck it on Friday night, was working fine deff woke up the turbo, after driving it for 2 days it's developed an misfire at 2.5-3k it drives fine until then, also feels like you can drive through it, anyone got any ideas? Or is it because there's to much fuel causing high pressure!

[londondan86]

12mm!! Bit overkill!

Is there air getting in somewhere, what's it like to start?

[dturbopeck]

Yeah mate I know, I just had the 12mm lying around, so thought I give it ago, it starts fine, tick overs fine, it's just at 2.5-3k it misses quite bad, unless it's got a dodgy seal in the pump,

[londondan86]

I would check for air getting in and replace the fuel filter first just to get the easy cheap jobs out the way

[Dave]

This is a common issue with 12mm heads, they are not a bolt on replacement like they are with 8/9/10/11mm heads...

[Tom]

I'd change the fuel filter, you described what mine does when running veg and the filter gets clogged. Its probably something more complicated though!

[dturbopeck]

The filters fine, not long been done,

It's just strange how it was running fine, then it went like this, I can quite easily swap it for a 11mm head but be nice toget to the bottom of this first

[londondan86]

This is a common issue with 12mm heads, they are not a bolt on replacement like they are with 8/9/10/11mm heads...

Never had a look at 12mm head, other than plunger size what's the difference Dave

[darrenjlobb]

Hm, the problem dosnt sound like it relates to the normal 12mm issue. Sounds like the pump is starving for fuel / sucking up air to me....

The 12mm causes problems as the relief port is orientated differently, meaning with standard levers you need like max fuel right in to even drive it, leaving lda little / no effect at all / hard to get good fuel AND an idle, problem is easily resolved with better levers... Ive done a few over the years.

[Piggy]

sounds like when my fuel filter is clogged on the veggy stuff...

so fuel starvation...which seems odd for a 12mm but not if Ruans right...which of course he is!

[Ruan]

I haven't posted yet!?

[Piggy]

I haven't posted yet!?

yeah but you will be when you do!

[dturbopeck]

Cheers guys, I will remove pump, replace all seals and levers, and see what happens,

[dturbopeck]

well got around to removing the pump again today, and it looks like it was my fault too, must of over tightened the throttle arm and its eaten through the washer on the bottom and eat halfway through gov cradle, and all the little bits of metal gone into the pump and damaged the cam plate and blocked the filter in the 12mm head, i will add a pic later,


so ive cleaned it all up, rebuilt it back up with all the levers, gov cradle and the top housing of the pump also left the standard lda pin in as its alot more agressive from the 12mm pump, now it seems to run fine but i havent drove it yet as i may as well do the brake master cylinder while the engine mount is off tomorrow.

[David]

12mm!! Bit overkill!

Have to argue

[Dave]

Pointless without bigger nozzles in reality, you're just massively pressurising lines without the nozzles allowing the fuel to pass. Long durations are what IDI's like, but 9mm is too small, with a tiny fuel port into HP chamber, 10/11mm pumps are where its at

[dturbopeck]

Pointless without bigger nozzles in reality, you're just massively pressurising lines without the nozzles allowing the fuel to pass. Long durations are what IDI's like, but 9mm is too small, with a tiny fuel port into HP chamber, 10/11mm pumps are where its at

Yep your right but as it was free lying under my bench I thought I give it ago, but I've also looked into bigger injectors

[con67]

Nice to see a pump being swapped the right way How long have you it down to?

[dturbopeck]

About 30 mins get it off, never done a straight swap for awhile, and I glue the woodruff key so it will never fall out on a swap

[londondan86]

About 30 mins get it off, never done a straight swap for awhile, and I glue the woodruff key so it will never fall out on a swap

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