carb or fueling issue - webers?

[twobone]

Hmmm.

 

90' Caterham xflow

 

I have this persistent problem. My car has a hard time starting when cold, it takes some serious applications of the throttle manually at the carbs to activate the accelerator pumps on the carbs and 3-4 attempts to catch.

 

It gets really bad once the car has been run, for example when I stop for gas. Often it takes a very long time to restart with again a ton of manual applications of the throttle bar at the carbs.

 

I'm starting to wonder about fuel pressure issues. When the car is running it seems to fuel quite well. Maybe some occasional stumbles on hard cornering or after hard braking.

 

Could I have a fuel pressure issue? Is there both a physical pump in the block as well as an electric one in the tank?

 

I'm starting to wonder if the electric pump in the tank (if one exists) has given up the ghost and that is why I'm not getting enough fuel pressure at rest? I assume once running the block manual pump is drawing enough, but at rest there is not enough pressure created with the starter to draw gas and start her (especially when she is warm)

 

thoughts?

[xcarguy]

I'll throw a few random ideas on the table for consideration. You may possibly have two unrelated/related issues; vapor lock and/or carbs that need some attention (rebuild/cleaning/adjusting). It could be a clogged fuel filter that simply needs to be replaced. I doubt you have two fuel pumps. If you had an electric pump and it quit, I doubt you would get any fuel to the carbs at all. Check the top of the fuel tank for the installation of an electric pump and trace the fuel line from the tank to the carbs in order too search for an inline pump . . . . just to be sure there is indeed no electric pump. Also, do you have any worn header wrap/heat wrap that may be adding to the problem by allowing increased underhood temps near a fuel line (vapor lock related)? Pull the fuel line off of the the upstream side (anywhere between pump and carb) of the mechanical pump and turn the engine over to see if you are actually pumping fuel.

 

Start with the simplest task (work from the tank forward). If your fuel pickup at the tank is on the tank bottom, disconnect the fuel line and check for trash. Change the fuel filter. If for some reason you have no filter, install one. If all checks between tank and mechanical pump (getting fuel to, and past, the pump) then time to address the carbs.

 

 

My two-three cents. :cheers:

[s2k7]

Take the fuel pressure....say 3 to 4 psi?

[coffee break]

My car has a solidstate fuel pump only. It starts pumping when the ignition is on. I let it run a few seconds before hitting the starter. Since I'm the 4th owner, I have no idea if it ever had a mechanical fuel pump. The electric fuel pump is one of those little cubes with a fitting on either side. It's mounted on top of the transmission top plate and gets 12v from the battery side of the coil, an easy hook-up. There is also a fuel pressure regulator set @ 2PSI.

It starts up without much fuss as long as I have the choke set right.

Hope this helps, good luck!

[twobone]

I think you are right. I've never heard any clicking with the key turned so I'm pretty sure I don't have an electric pump. I will replace my in-line fuel filter and check the weber in-carb filters and double check the float and ball/needle. I also wonder about vapor lock, but it happens when the engine temp is normal and hot. Its a relatively new issue and so I'm hopeful its just something gunky

 

 

I'll throw a few random ideas on the table for consideration. You may possibly have two unrelated/related issues; vapor lock and/or carbs that need some attention (rebuild/cleaning/adjusting). It could be a clogged fuel filter that simply needs to be replaced. I doubt you have two fuel pumps. If you had an electric pump and it quit, I doubt you would get any fuel to the carbs at all. Check the top of the fuel tank for the installation of an electric pump and trace the fuel line from the tank to the carbs in order too search for an inline pump . . . . just to be sure there is indeed no electric pump. Also, do you have any worn header wrap/heat wrap that may be adding to the problem by allowing increased underhood temps near a fuel line (vapor lock related)? Pull the fuel line off of the the upstream side (anywhere between pump and carb) of the mechanical pump and turn the engine over to see if you are actually pumping fuel.

 

Start with the simplest task (work from the tank forward). If your fuel pickup at the tank is on the tank bottom, disconnect the fuel line and check for trash. Change the fuel filter. If for some reason you have no filter, install one. If all checks between tank and mechanical pump (getting fuel to, and past, the pump) then time to address the carbs.

 

 

My two-three cents. :cheers: