Fuel issue

[B_Conolly]

All,

Wondering if anyone can assist with diagnosing a fuel problem that I have been banging my head against for the last couple of days.

Recently rebuilt the engine in my 85 2ltr 116 with bits from Vin Sharp. Car has been sitting for nearly two years. Started up the engine with no problems, lift the rpm to somewhere around 2000-2500 to run in the cams and then tuned it up a little. Engine ran with no problems for 20+ minutes with the exception of a couple misfires but nothing too unusual.

Cleaned up the engine bay and then fired it up for a test run - it was almost cold by this point. The engine was running for around 5 minutes and then the rpm started to fall sounding a lot like fuel starvation and then stopped. Removed the hose on the tank side of the fuel pump and it was dry. Removed the fuel pump and a quick inspection by Marc at Milano resulted in me purchasing a new replacement pump. The arm in the old pump was almost fully compressed but it did have about 5 mm of movement in it.

Installed the new pump and primed the lines but still no go. It ran for about a minute then stopped, again no fuel on either side of the pump. Removed the regulator/filter and fitted a clear filter to eliminate the reg. I pushed a little air in the tank by blowing into the hose that goes into the negative side of the pump (definitely no blockages from the pump to the tank), the tank was then pressurized and the new filter started to fill up with fuel. The engine then ran for about 3 minutes and stopped but there was fuel on the tank side of the pump.

Checked the reg and filter and both are ok, no blockages. Primed the lines and reg and now I have fuel on both sides of the pump and reg (dribble) however NOTHING in the lines to the carbs. The engine will start (eventually) and idle for 3-5 seconds. Pressing the throttle will result in the engine trying to increase rpm but stalling. I can hear fuel flowing from one of the carbs when pumping the throttle but not both....?

Before I start looking at the carbs what procedure should I be using to eliminate everything from the reg to the tank ?.

Should there be pressure in the tank ?

If I remove the line to the reg from the pump and crank the engine should the fuel flow noticeably and should removing the line to the carbs produce the same result ?

Would very much appreciate any assistance with this, really hoping to the GTV to winton next week with my 2 yo.

Regards,
Bret

[MD]

Superficially sounds like you have developed some deposits in the tank whilst the car was idle. These have worked themselves up through your fuel supply system. From your description you have tackled some components but not everything.

I would suggest a tank to inlet port check and clean everything and installing an in line filter between the tank and the pump to prevent a recurrence.

It cranks,it fires, it runs but runs out of fuel so concentrate on fuel delivery from start to finish.

[Typhoon90]

It's pretty easy to blow out the fuel line from the carbs to the tank, disconnect fuel line at tank, disconnect at carb and blow compressed air through line from carb back.
I'd also look at the needles & seats on the carbs, very common for them to stick up when they've sat for a while and also for chunks of crud to lodge in there when first started.
If teh car sat a couple of years, I'd probably disassemble the carbs and give them a good clean.

Regards, Andrew.

[B_Conolly]

Thanks gents. Decided to give the fuel system a good going over based on your suggestions, have to work fast .

Is it possible to break the lobe on the oil pump via the fuel pump ?. Just to be sure....

Regards,
Bret

[MD]

Bret,

Anything is possible but if the car runs and dies, this is not likely. However, the fuel pump diaphragm can fail and the internal valve seats may have build up on them preventing a good seal. Take the fuel pump apart and check for these things. The simplest solution  to check pump operation is to swap a known good one for yours and try again.

Dont overlook previous advice already given by me and Andrew.

[B_Conolly]

"The simplest solution  to check pump operation is to swap a known good one for yours and try again." I am tattooing this to my arm...

Ok, I removed all lines and gave them a good clean with the compressor from carbs back. Installed new in line filter just before the tank. Removed the new pump and noticed that the arm inside the pump on the diaphragm side was in several small broken pieces.

Back to Marc at Milano tomorrow lunch time

The pump must have been stuck open enough for the pressure in the tank to push just a dribble of fuel up to the carbs *shrug*.

Had a very close look at the carbs, needle and seats tested good.

Problem not solved as yet but at least making some progress.

Thanks guys !!!!

Bret