Web
Analytics Made Easy - Statcounter
Fuel pump pressure? - Page 2 - Engine/Ancilliaries - The Lotus Forums - Official Lotus Community Partner Jump to content


IGNORED

Fuel pump pressure?


Recommended Posts

  • Moderator

From the detailed description you've given, it seems it can only be a leaking valve in the float chamber. This can happen after a rebuild (been there...), or there was an underlying cause that wasn't rectified during the rebuild. As above, be very careful and try to make sure it doesn't happen with just ignition on. Cranking doesn't result in much change in vacuum, certainly no boost will be built, so it's unlikely to affect fuel delivery.

I also think the non-starting issue is a result of the flooding, and not the other way around. Even new plugs will struggle to ignite an overly rich mixture and they can very quickly foul and remain bad even after cleaning.

  • Like 2

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to comment
Share on other sites


Upgrade today to remove Google ads and support TLF.
  • Gold FFM

Thanks yes I will take the carbs to a proper carb servicing place but they’re hard to find these days. 
 

One last question.  Should the engine start at all with no plenum attached or are all the vacuum pipes etc mandatory for the engine to start?

Link to comment
Share on other sites

  • Moderator

Not saying you can't fix the carbs yourself, just that you need to have another look. 😉 One test I often do is to blow through the fuel line, both with the float valve open (to make sure it isn't blocked) and with the valve closed, to make sure it actually seals.

If everything is set up correctly, the engine should start or at least show some signs of life with the plenum off. If it does start, it won't idle properly of course without the necessary vacuum connections. I don't think there is much to be gained by trying this, unless you want to verify if the leak gets worse when cranking and where exactly it is coming from. My advice would be to have someone else there to assist, so you're never in the car turning the key when there is potentially fuel spraying in the engine bay.

 

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to comment
Share on other sites

  • Gold FFM

HAVE I FOUND THE PROBLEM!!!

Having removed the carbs and (again) checked the float valves/needles etc, I turned them upside down and spotted something (see pics).  One of the accelerator pumps is different to the other one and doesn't allow the release of the plunger (see how far the adjuster nut is wound in compared to the other one.

Could this be the cause of all my problems???  What does this actually do and which one is right?

IMG_1459.JPG.c11c7aca035a9071590728d0a866b30b.JPGIMG_1458.JPG.eb2b3aa82b8765513309f427fe7ec8e4.JPG

Link to comment
Share on other sites

Hmmm but that wouldn't dump fuel via the plenum? - However, its probably worth checking the diaphragms under those covers for completeness.

The nut position on the rod is the pump volume adjustment.   Good adjustment is material to smooth acceleration, so I would check that out as they look imbalanced.   There are posts on here how to do it.   I used a fairly crude but accurate set up, others have made more sophisticated versions of the same thing. 

 

  • Like 1
Link to comment
Share on other sites

Here's my theory... One of the pump jet valves (the ball & weight under the top cover) were not seated correctly, or had some debris in there and you were forcing fuel out of the pump jets   

Link to comment
Share on other sites

  • Gold FFM

Thanks Steve, I agree, maybe this accelerator pump isn't my issue then.

My theory now is that when the car wouldn't start (due to a distributor issue), the constant attempts of starting have flooded the engine big time (when I removed the inlet manifold, 2 of the valve chambers were full of fuel - but this was the back carb (which wasn't leaking)).  The front 2 valve chambers were dry.  This is the carb which was leaking. 

So maybe, for some reason, the back carb has been sending fuel down the chambers, and the front carb has been (for whatever reason I'm still to establish) not allowing the fuel into the inlet manifold but backing up backwards and leaking from the carb and forcing it back into the plenum.

Which would be the correct outcome for an engine flooding?  Filled up fuel in the inlet valve chambers, or not, and to force the fuel elsewhere?

Link to comment
Share on other sites

  • Gold FFM

Hi guys, i'm still here and still with a non starting car :(

Once again after failing to start, I've stripped everything down to the inlet manifold, and once again, I find fuel sat in the inlet ports of 5,6,7&8 (see pic).

image.png.6480f7af0aba32fec8624aee3ec4b148.png

IMG_1489.JPG.149b861729c013f48b19fd7ffe9e0c06.JPG

Is it at all possible I have some inlet valves stuck?  I mean when turning it over, surely this fuel would have fallen into the combustion chamber?

I've never taken an engine further than this - ok rocker cover off etc, but never had cams off etc.  Do valves stick?  How can I check they're opening?  If I were to put the endoscope down the port and jack up rear wheel in 5th gear and turn it, should I see the valves opening and closing?

I've dried up the fuel with cloths etc and all is now clear, and I've had an endoscope down all the inlet ports and all looks ok (a little bit of fuel) but nothing major and I've had the endoscope down the spark plug holes and all looks fine there too (not soaking wet like I thought it might be).

Inletvalve.png.0913b905cde17c4377b89a5437e256bb.png

I'm starting to lose the will now........it's been weeks I've been trying to sort this, and a small fortune on new bits (new distributor, new coil, new FPR, new gaskets, full carb service kits, new plugs, etc etc) lol.  At least it's been a good learning exercise - or it will be when I finally get to the bottom of my problems!

 

Link to comment
Share on other sites

  • Gold FFM

About 3 weeks ago.

But I believe I’ve had a number of issues. One was the distributor but that’s sorted and I definitely have a spark. Ok timing could be a bit off but it should at least start or try to fire at least. 

Link to comment
Share on other sites

  • Gold FFM

Does it still flood with fuel with ignition on?

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

Link to comment
Share on other sites

  • Gold FFM

Leave it pumping for a minute or two; you'll find out!

You have to determine whether it leaks in this situation.  I remain convined it's the float valve in carb #1.

  • Like 1

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

Link to comment
Share on other sites

  • Gold FFM

Everything is off now (for the 3rd time). Ideally I’m not putting it all back together until I know what’s what.

I know what you mean about the floats and I will be doing tests on these before putting back together 

Link to comment
Share on other sites

  • Moderator

Yes, you should see the valves move if you turn the engine by hand or by rotating a wheel. If you take a cam cover off, you'll also see the cam move and the tappets under the lobes come up and down. But sticking valves wont result in flooding like that, as little or no mixture will be sucked in. So the fuel must be pushed from the carbs to the inlet somehow.

With the carbs off again, I would try reconnecting the fuel lines, put the carbs more or less level and turn on the pump (either with the ignition key but even better by putting a jumper in the relay, that way nothing else will be live). If there is a leak, it will be obvious where exactly, so you know what to look at next. Float valves still the prime suspect.

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to comment
Share on other sites

  • Gold FFM

Thanks both. I will certainly give the float valves a full check tomorrow and even thought the needle valves are brand new I will recheck these - it’s important to know that it has done this prior to me servicing the carbs so I haven’t created this, but also the carb servicing hasn’t fixed it either (I’ve literally had every single jet out and the carbs in a 100 pieces) and it’s still doing it.
So I’m not sharing your gut feeling that it’s the carbs causing this but I’m also not ruling it out.

I’ve 100% got 4 PSI fuel input and a new FPR to boot. 

In addition to the float valve checks, tomorrow (now everything is dry) I will

1. Jack up and turn the wheel and see if I can see the valves rising with my endoscope.

2. Turn off the fuel pump with the inertia switch and spray easy start into the ports, crank it and see if I can at least get the engine to fire.  

3. Reattach the carbs, press the inertia switch and turn on the ignition for the fuel pump to start (coil disconnected so no chance of a spark) and have a look through the carbs to see if I can see fuel coming through. I won’t press the accelerator at all. 

4. Crank it (still with the coil disconnected) and check again to see if I can see fuel leaking out anywhere. Again I won’t press the accelerator at all  

5. Take carbs off and see if any ports are full again.  If dry I will repeat 3&4 but with the accelerator pumped a couple of times  

I will report back on all points (with pics and videos if possible). 
 

Are there any other checks I should carry out?

Link to comment
Share on other sites

  • Moderator

My 2cents:

2. wont tell you much, if the engine is flooding it wont start and plugs are likely fouled. While start pilot can be useful for to determine if fueling is causing problems, it's easy to get carried away trying to get it to start and you wont be doing your engine any favors by spraying something similar to degreaser into the intake. 😉

3. why not try with the carbs detached? Just to save some time an effort. If there's no sign of a leak, you can still attach them and continue as planned.

Good luck!

 

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to comment
Share on other sites

Bear in mind that its likely the bores will have catastrophic amounts of fuel sitting in them (or drained into the sump....)  Take the plugs out and spin the motor over - with the fuel pump disabled via the inertia switch to get rid of as much fuel as possible.   Also consider changing your oil if dipstick high or oil smells of fuel.

Not sure you need to start looking at valves etc unless its hydrolocked and somehow stripped the cambelt - but that wont be the case...

Its 100% a carb issue - The possibilities:

  • A mechanical issue (eg a crack in the body - but I've never heard of that)
  • You have pumped the throttle a 1000 times - but that would affect both carbs
  • The float valve is not functioning/seating correctly - or perhaps the o-ring is omitted from the valve seat (or is it a washer - can't remember!).   (floats could also leak in the old days, but don't think that is a 'thing' with dellortos)
  • Finally, fuel is bypassing the normal pilot/mains circuits when fuel pressure is present - EG if the valves for the accelerator pump circuit were not present or assembled incorrectly.

With the carb off the car, assuming the float bowl is full, fully deflect the linkage and you should see the 2 pump jets spray a very neat jet of fuel for a metre or two!   If not, that suggests an issue with that circuit.   

I'd also jerry rig the offending carb off the car to see if you can recreate the problem off the car, with elevated fuel pressure, shaking it around etc.   But even if you cant, I'd be rebuilding it again!

 

 

 

 

Edited by 910Esprit
  • Like 2
Link to comment
Share on other sites

  • Gold FFM

Thanks again guys. I’m only doing 2 to eliminate another issue which is timing. I’ve replaced the distributor whilst all was off so I would like to confirm that at least the engine would fire. 
Also I’ve had an endoscope down the spark plug holes and they’re dry, which again made me wonder if the valves weren’t opening on these ports (I know unlikely) but if the ports were opening why would the fuel be just backing up in these ports?

Link to comment
Share on other sites

  • Gold FFM

Ok, number 1 complete - valves opening normally

 

BUT - pulled the dipstick out and it stinks of petrol!  Looks like an oil change is needed - have I done anything serious by this happening?  Should I flush the engine oil at the same time or just a regular oil change?  Any recommendations for oil type?

I'm not proceeding with 2 at the moment then, I'll skip and go onto 3.  Whilst I'm at the car shop buying oil, I'll get some long fuel hoses, so I can carry on with 3 off the car so I can properly look at what's going on inside the carbs

Link to comment
Share on other sites

9 minutes ago, Maggo54321 said:

Should I flush the engine oil at the same time or just a regular oil change?  Any recommendations for oil type?

I think you've already flushed the engine with petrol so I'd just let it all out, change the filter & refill with the recommended oil

  • Like 1
  • Thanks 1

Cheers,

John W

Link to comment
Share on other sites

  • Gold FFM

Right guys.......carbs on a bench near the car.  Fuel pump on.  Petrol pissing everywhere out of the back carb within 5 seconds, not a drop from the front one!  Coming out of the front and the back (and the little hole at the top) on both chambers.  Basically everywhere, explains why plenum full as well as inlet ports!

 

 

 

Link to comment
Share on other sites

  • Gold FFM

But, the needle valve is working!

Here's a picture of the top of the carb turned upside down (and the fuel pump is on at this photo).  Nothing at all comes out.  The gap between the float and the gasket is 15mm

IMG_1507.JPG.cbf3ccc1a8e0bc6d6e0f48bd3947f09b.JPG

IMG_1508.JPG.fa3908b10c477d3479c6f71fd41d1e9f.JPG

 

Link to comment
Share on other sites

  • Gold FFM

I swapped over the tops of the carbs to eliminate things (including the floats) and miraculously it's stopped!  Maybe its getting stuck somehow, but I'll keep on trying it tonight for a few hours just to get it consistently working without leaking.

Someone has said that the jets (when throttle applied) would squirt fuel for 2 metres?  I've tried this and the jets squirt downwards, not forwards.  Is this normal?  Here's video where you can just see it if you look in the venturi past the butterflies.

 

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We use cookies to enhance your browsing experience, serve personalized ads or content, and analyze our traffic. By clicking " I Accept ", you consent to our use of cookies. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.