2a Possible fuel starvation

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Looking at a friends 2.25 petrol 2a tomorrow with 4 year old weber carb. It keeps dieing when warm. I'm presuming fuel starvation due to lack of fuel in the inline filter.

From cold, I hand prime the lift pump and it fills the inline filter to the carb about 1/4 to 1/2 way. Engine starts fine and all is dandy until it hits N temperature.

When it's fully warmed up, at N, fuel is no longer being refilled in the inline filter. If i go to hand prime, then it pumps one or twice, then goes soft.

So, as i'm going to be miles away, up in the hills, outside in the freezing cold anyone suggest a bunch of things i can check.

Carb is not hot, just slightly warm to touch when warmed up and the fuel lines don't feel hot.

Couple of ideas's that pop into my head.

  1. replace the lift pump with a stripped and cleaned donor.
  2. vent cap knackered, so tank vacuum.
  3. vapour lock, dodgy fuel? or fuel line hot by lift pump
  4. dirt in the lines.
  5. tank pickup clogged
  6. air getting into system
  7. carb float acting up

any more pls gents :)
 
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Got to be honest I'd go straight to 1 after a check of the lines for loose connections. This sounds like a cracked pump diaphragm - works when coldish but when the fuel gets at it it goes limp (oo 'eck!).

A floating bit of junk in the tank would be much more intermittent and hard to trace, and usually loose connections are not all that related to temperature.
 
Er, yes. But search for previous threads there's information there. I'd say that is probably your problem. Hot mech pump leads to vapour forming in the valves in the top of the pump body where the valves are.

To test theory borrow / buy a facet fuel pump <7psi and a pressure regulator (set to 2.5 psi) you can quickly rig this up under the driver's seat / near tank pushing fuel through the current pump if you're surre its not leaking.

If that cures problem then a proper fitting you should remove mech pump (if that fails you don't want to pump a load of petrol into the sump!). I've also fitted a relay that cuts the fuel pump if oil light comes on, with a button to bypass. The idea here is that if you have a roll-over the pump will stop.

D
 
Given the temperatures lately here and in the UK (and assuming Scotland hasn't been moved to Saudi Arabia) I am really reluctant to even guess at vapor lock. Typically that takes nasty high underhood temps - and given the open design of a Series truck I'd be very surprised to see that pump be any more than warm to the touch even after a good hard run.

I've never heard of a case of it in Winter except when coupled with a cooling-system failure on a vehicle with a carb throat heater in the coolant path.

ajr
 
I'm pretty happy that I'd confirmed it. The pump is bolted to the side of the block and will quite quickly heat up to very close to the engine temp. I suffered problems right down to winter temps of -10 to -15C though it was much worse in summer. The problem is due to the new ethanol fuels (and their additives). Problems tended to be worse if the truck stood with the engine off (or with fan stopped with electric fan) due to there being now air flow.

However, if you don't want to believe me, even though I spent weeks confirming this (including 3 fuel pumps, new pickups, new fuel lines, pumps pressure and leak down tested etc etc) and a double check by going back to mech pump to confirm you don't have to.

For a £60 pump and regulator I can now rely on my motor to work reliably and not pull the stunt that it used to, stalling just as you try to join the motorway after being stood at service station. Nearly killed me once!
 
back, cheers for the replies, might have a look at the leccy pump.

stripped the lift pump out and it had three little tears, so i swapped the diaphragm with another, fitted it and it was pumping much better.

then took the carb top off and found some crap in the chamber, so gave that and the jets a good clean with air and spray. The float valve seemed to stick a little, so i gave that a good cleaning too.

it then worked much better to N and didn't stall this time. I thought I was done but he said it doesn't always happen yet..

so, I then let him do what he does :eek:

someone has fitted a leccy kenlowe but they have wired it so it comes on when cold and off when 1/4 warm. How useful!

It turns out he isn't switching the kenlowe override on and is letting the engine get to a bit under the red. This in turn is causing vapour lock in the pipes. :doh:

so i've told him to manually switch it on at N and ordered some leccy bits to rewire it properly.
 
Smart, sounds like you are getting closer!

I'd be tempted to change the oil if there was any sort of leak in the diaphragm, it's easy enough for petrol to get into the sump with the cam-driven pumps and make the oil very thin.

See how he gets on with a working fan. The best test that it is all well is to go for a proper race round until everything is properly hot. Then park up for five minutes at the bottom of a long uphill drag and see if you can make it to the top without it cutting or stalling.

D
 
dominicbeesley said:
Smart, sounds like you are getting closer!

I'd be tempted to change the oil if there was any sort of leak in the diaphragm, it's easy enough for petrol to get into the sump with the cam-driven pumps and make the oil very thin.

See how he gets on with a working fan. The best test that it is all well is to go for a proper race round until everything is properly hot. Then park up for five minutes at the bottom of a long uphill drag and see if you can make it to the top without it cutting or stalling.

D
Click to expand...

good ideas. i'll give his oil a sniff next time and check for contamination. :)
 
Not to hijack your thread, but I justed fitted a electric pump in mine last week. I used a generic pump - I tested a max of 5-6 PSI (vacuum) on it and it did leak out of the zenith just a bit if I left it run. My brother in law made a custom bracket for it just forward of the fuel tank on the side of the frame. Its conected in series to the mechanical pump and wired to a bosh type relay. A red iluminated momentary switch on the dash is connected to the relay. I thought it would cure my vapor lock problem, but it does'nt help as much as I expected. A new battery helps too if the cranking speed is slow. I thought I could push the momnetary button until I hear the pump stop (clicking) unable to push anymore petrol through the system, and my landy would start on the hotest of days, in direct sun, and a hot start. Mine starts in 1 sec when cold, and more then 30-40 seconds when hot starting if the battery lasts.
I also wanted to hook up to the oil light as mention by dominicbeesley, but I had vapor lock in my brain when doing the wiring.heh
Anybody try a inslulated sleeve to go over the fuel line from mechanical pump to zenith?
I would never guess vapor lock in the winter time, at least for you trax you would only have to pull over every once in a while and throw some snowballs under the hood.:) I can almost fry a egg on the dash sometimes when stuck in traffic. I cant believe thats normal :eek: lol
 

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just to update this. when going over it i spotted a few issues that needed sorted.

i rewired the fusebox.
refurbed the lift pump.
replaced split ht's
cleaned up rotor arm
new fuel filter
cleaned dirty carb
noticed the kenlowe was wired incorrectly and not coming on, so rewired that
spark gaps were huuge and they were a bit worn, so stuck new ones in

it's all sorted and where it used to take a good few cranks to get it going, it's starting first time.

i think the problem was down to a dirty ass filter, lil split in fuel pump, engine overheating and the spark gaps increasing until they didn't work.

all sorted now though :)
 
CakeBandit said:
Not to hijack your thread, but I justed fitted a electric pump in mine last week. I used a generic pump - I tested a max of 5-6 PSI (vacuum) on it and it did leak out of the zenith just a bit if I left it run. My brother in law made a custom bracket for it just forward of the fuel tank on the side of the frame. Its conected in series to the mechanical pump and wired to a bosh type relay. A red iluminated momentary switch on the dash is connected to the relay. I thought it would cure my vapor lock problem, but it does'nt help as much as I expected. A new battery helps too if the cranking speed is slow. I thought I could push the momnetary button until I hear the pump stop (clicking) unable to push anymore petrol through the system, and my landy would start on the hotest of days, in direct sun, and a hot start. Mine starts in 1 sec when cold, and more then 30-40 seconds when hot starting if the battery lasts.
I also wanted to hook up to the oil light as mention by dominicbeesley, but I had vapor lock in my brain when doing the wiring.heh
Anybody try a inslulated sleeve to go over the fuel line from mechanical pump to zenith?
I would never guess vapor lock in the winter time, at least for you trax you would only have to pull over every once in a while and throw some snowballs under the hood.:) I can almost fry a egg on the dash sometimes when stuck in traffic. I cant believe thats normal :eek: lol
Click to expand...

are you deffo getting vapor? is the inline filter empty?
 
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