Shitbox Rally Pug 405 SRDT 94 starts but won't run

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Erikbm

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Fellow Frogger
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Wollongong, NSW
Hi All, I have bought a non-running 405 diesel for the spring Shitbox rally. It was a deceased estate and looked like the owner pulled off the fuel filter and then didn't get around to doing any more for the next 10 years. I put an aftermarket filter in and can get it to start, but it only runs long enough to get it out of the driveway and onto the street and then it loses power and runs really roughly for a minute before dying.

It could be an air leak in my new fuel filter, but before I make it absolutely air tight, is there a 2nd fuel pump at the tank which primes the whole thing???

Regards, Erik BM
 
If the filter was out for years the situation is like running out of fuel, only worse. It will need full bleeding.

If you have a CAV/Roto injection pump it will like an old LandRover IIA - clean the bleed on the filter, open it and let the starter pull up until clear. That's usually enough, BUT...

---this car has been abused. Still using LandRover technique, the injection pump also has a bleed screw, and may need bleeding using the hand pump if present. In the worst case the distribution pump will have been fully drained, and then there is also a bleed screw in the control cover to attend to.

The pic is from the Roto handbook.
alimentation.jpg
 
Whatever you do, don't dismantle the pump. With extreme tolerances it's a specialist operation. This thing is one of the cleverest all-mechanical devices you will come across. Roto made the CAV pump under licence.

Attached are pages of the CAV pump manual, which may help.
 

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  • p7a.pdf
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Hey Erik, we are doing the Autumn 2024 Shitbox! This will be our 5th...Great event, I would love a 405, let me know if you want to sell it.
 
Sounds like an air leak somewhere, I had a 405, and i remove that squeeze bulb primer and replaced it with an electric fuel pump, the low-pressure type for carburettor engines. Fixed all the issues I had with mine. The bulb can in suck air, and the 3 psi from the fuel pump helps with starting and high load conditions.
 
If the filter canister was left out for years there is likely to be air everywhere, similar to a system rebuild. I worry that if air, or worse, water vapour, has got into in the pump for years there may be corrosion of the almost no clearance parts..
 
Sorry, I didn't include the diagram showing bleed points as described in the CAV manual.
I have a P405 manual, but it doesn't describe the full procedure after a dismantling/drain out - just the simple bleed case after fuel tank empty.
.

bleed points.png
 
If it runs, why don't you crack each injector one at a time for a period of time, this should allow any air on the high pressure side of the pump out.

I've had this issue with a couple of cars now. Both times replacing the primer/filter assembly to prevent air entering the suction side of the pump fixed it. I just went to the local wreckers and got *any* diesel pump/filter assembly and fitted. so long as the lines fit, it should work.
 
That sometimes works, particularly when there is a lot of fuel in the system, but can take a lot of cranking. If the pump needs priming, it is best to do it on the pump.
 
seasink said:
That sometimes works, particularly when there is a lot of fuel in the system, but can take a lot of cranking. If the pump needs priming, it is best to do it on the pump.
Click to expand...
I meant something like this.

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It has a built in primer you can use to bleed the system... you need to remove the old primer/filter assembly as it'll likely be leaking air.
 
The CAV distributor pump system doesn't need it. Normally a simple bleed at the filter does the job, with the injection pump sucking fuel. The filter is a cartridge that fits into a sealed housing at both top and bottom. Some systems like LandRover also include a separate water trap with a similar but transparent cartridge.

The filter bleed point won't clear a pump with air in it, hence the bleeds on the pump. One is in the high pressure area and usually isn't needed.

The pump is a masterpiece of design, now quite long in the tooth, with no internal ball or roller bearings or gears and is lubricated by the fuel. It provides equal charges to the cylinders in the correct order, with the quantity determined by a governor. Automatic advance is catered for.

The device is quite different from the Bosch type seen on most non-common-rail engines.
 
seasink said:
The CAV distributor pump system doesn't need it. Normally a simple bleed at the filter does the job, with the injection pump sucking fuel. The filter is a cartridge that fits into a sealed housing at both top and bottom. Some systems like LandRover also include a separate water trap with a similar but transparent cartridge.

The filter bleed point won't clear a pump with air in it, hence the bleeds on the pump. One is in the high pressure area and usually isn't needed.

The pump is a masterpiece of design, now quite long in the tooth, with no internal ball or roller bearings or gears and is lubricated by the fuel. It provides equal charges to the cylinders in the correct order, with the quantity determined by a governor. Automatic advance is catered for.

The device is quite different from the Bosch type seen on most non-common-rail engines.
Click to expand...

Interesting, the XM pump must have been a bosch pump. It would draw air through the filter/primer bulb assembly.. I thought the 405 would be older technology than the 12valve diesel in the XM!


index.php


I would have popped in a new filter/primer assembly, opened the bleed screws on the top of the filter housing, pump until no air.... opened the bleed screw(s) on the pump, pumped until no air .... then cracked an injector line while cranking to bleed the high pressure side.
 
If someone hasn't told you, you would not suspect the location of the pump bleed points. The filter and injector spots are common to most diesels.
 
seasink said:
If someone hasn't told you, you would not suspect the location of the pump bleed points. The filter and injector spots are common to most diesels.
Click to expand...
are they hidden between the block and pump? I sure do believe you are right I wouldn't have found them though! I've been bitten to many times now to say confidently "Yeah I'd find something" :clown:
 
1683789335855.png
It isn't that CAV pump Seasink, it is this one. I have opened a few things that looked like bleed points and got some air out of them, but to no avail. It starts, runs fine for 10 seconds and then stops. If I wait 2 seconds and crank it again, the same thing happens. I have also cranked it for a bit with the injector nuts loose, but get the same result.
 
I though we got CAV-Rotos. Sorry.
Here is some stuff about the Bosch pump.
p1.png

p2.png
 
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