Odd running problem, suggestions please!

Cappo · Post by **Cappo** » Mon Feb 18, 2013 8:40 pm

I picked up a Land Rover 90 at the weekend which is running an ex-Range Rover 3500 V8 on Stromberg 175 carbs, along with an LPG conversion. It was sold as "running fine on gas, but really badly on petrol". The actual version was that it started and ran on gas, but not very well, and not on petrol at all.

I started looking around and trying to find the problem, and found pretty quickly that the 4 cylinders which the RH (offside) carb feeds were not running at all (ie 2,3,5 &

. I haven't yet been able to work out whether the gas is getting to the mixer ring OK, but I assume it is as the gas comes off the vaporiser and splits just before the carbs. I can check that by swapping them over anyway.

The strange thing is that if I remove the air filter and put my hand over the intakes, the vacuum/suction is MUCH (and I mean MUCH) stronger on the nearside carb, the one which is running. I've done a compression test and the values are pretty even across all 8 pots at around 135 psi - probably a little low but this was stone cold, throttle closed, no oil, and was done mostly to look for any major differences. Also I believe the old Rangie motor was the low-comp version anyway (?).

I also took the LPG mixer rings off and rigged up a temporary petrol supply to try and run it solely on petrol but it wouldn't start at all.

I've had a hunt around for vacuum leaks and not spotted anything yet. So I guess the next step is to strip the carbs and clean everything out and start from scratch.

But if anyone can offer any other thoughts, suggestions, ideas, experiences, etc etc etc then I'd appreciate it!

Cappo · Post by **Cappo** » Mon Feb 18, 2013 8:43 pm

I should also add, the various breathers have all been completely chopped about - some are missing completely, some are blanked off (with bolts!) and so I need to work out how that all needs to be put back in place as well. But would this affect the general running?

ChrisJC · Post by **ChrisJC** » Tue Feb 19, 2013 7:28 pm

Check the diaphragms in the carbs - I believe they are rubber in the Strombergs and can perish.

Chris.

bigaldart · Post by **bigaldart** » Tue Feb 19, 2013 9:32 pm

I agree, a damaged Stromberg diaphragm will not lift the needle and slide at all and not let any fuel or air in that carb.

Alan

Cappo · Post by **Cappo** » Wed Feb 20, 2013 11:27 am

Thanks gents. I did check the diaphragms and couldn't see any holes or splits, but I have bought two spares and will replace them to see.

I'm starting to suspect that the problem is actually down to the carbs being so far out of balance that only one is working. Have also found a problem with the fuel supply (currently running it from a temporary bottle/tank) so I'll get that done first then try again.

Big woof · Post by **Big woof** » Wed Feb 20, 2013 12:31 pm

You can buy vapourising rings that auctually bolt on to the carbs also check the oil in the dash pots as these can be fillied with engine oil and don't lift up at all. Fill them with a thinner oil like ATF I found was best. Balancing the carbs may also help the running problem and also make it a touch more economical. Reconnecting the breathers may also help the running problem.
A very good service can help but one thing is getting the gas set up right to be able to get a good running engine on lpg that might be best left to a professional