Fuel delivery

[ggenovez]

Hi all,

I'm still fighting my carb issue I posted a few days ago. The car starts and dies or by feathering the pedal I can get it to run for 3-4 seconds @3000 RPM before it stalls again. Then pumping the pedal it starts but has the same problem.

I'm thinking the fuel pump might be an issue.

What PSI should I look for and how much fuel should come out when I crank? Is there a measure for this? 1 cup every 10 seconds of cranking or something?

[mosu]

I temporarily experienced the same symptoms. I had recently installed a new Meyle fuel pump and I thought it may have gone bad. I pulled the carb inlet line before and after the fuel filter and cranked the car. The pump delivered a strong gush of fuel. I don't know what the official measure is, but if you're getting the "strong gush" every turn of the engine, the pump is probably OK.

Do you have any air leaks around the base of the carb or the throttle shafts? Do both throttle shafts close completely (ie: the carbs are idling through the idle circuit only)? My secondary was hanging open creating a big air leak.

I'm not very experienced with the Zeniths, but I would start there. Hopefully a more experienced member can chime in as the answer would help both of us.

[ggenovez]

What I saw was less than stellar. Pointing the fuel line up, I saw a mediocre 4-5 inches of fuel shooting up. I was not very impressed.

This was with a new fuel filter as well.

[mosu]

Sounds like it's working fine. That's what I am seeing as well.

[Jub]

You can buy an inline fuel gauge from autozone that will show you immediately (and in real time), if you have a fuel pump issue.

I loooovvveee this thing, no guessing needed: 15 bucks, 15 min install...I would highly recommend it for all carbed engines. This simple set up will tell you: 1. If you have a faulty fuel pump (yes/no), and 2. how much pressure is being delivered (too much/ too little).

Also, what is cool is you can hook up a fuel pressure regulator as well farther down the line you can set it to exactly what pressure you want, and looking at the gauge farther upstream you can verify that your regulator is spot on (autozone as well ~20 bucks). FYI: I have webers set to 2.5 psi.

Once you've ruled out fuel issues, you then know it is probably a vac leak (went through this process myself...found the leak where my carbs sat- hairline crack in the gasket, as mosu hinted about)

[Jub]

Here's a pic of the fuel pressure regulator.

Always remember at the end of the day the fuel going into the carb at the correct pressure is what counts. So, in terms of the layout: put the regulator on after the pump, and the gauge on close to the carbs (ie, pump...filter...regulator................gauge...carb)

Lastly, this will also tell you if your filter has issues as well!

[ggenovez]

Thanks Jub, I'll definitely look into those.

I have one of those craftsman pressure guages and It's barely reading 1 PSI. Think I found my problem

[ScooterABC]

After it dies, you might want to open the top of the carb(s) and look and see if the float bowls are empty.

[ggenovez]

The fuel pump is intermittent. I disconnected the fuel line and cranked and nothing happened or it will pump a shot every 10 seconds or so.

Removing the return line and pumping in some compressed air, the car fired right up and stayed running 3-4 seconds. Much longer than before....

[mosu]

What if you route the pump inlet/outlet to a jerry can full of gas and watch it pump in isolation from the fuel lines on the car?

If it's consistent, there's an upstream blockage. Perhaps the length of rubber hose that connects the fuel tank outlet to the hard fuel line leading to the engine compartment has collapsed internally?

[n10]

Originally Posted by Jub

Here's a pic of the fuel pressure regulator.

Always remember at the end of the day the fuel going into the carb at the correct pressure is what counts. So, in terms of the layout: put the regulator on after the pump, and the gauge on close to the carbs (ie, pump...filter...regulator................gauge...carb)

Lastly, this will also tell you if your filter has issues as well!

Sorry to butt in but ...Hey Jub

Where did you get that regulator from?

[Jub]

n10,

I bought mine from some place in Europe a year ago-ish, it was like Mc -something or others (took like 2 weeks to get it). But then one day I was in autozone and saw one similar on shelf. Turns out there pretty universal. They have a dial which you can set in 0.5 psi intervals.

I just briefly checked eBay and they have them there too (you want one that can be set in lower range psi 0.5-6-ish (weber carbs run best around 2-4psi):
Fuel Pressure Regulator Dune Buggy VW Baja Bug | eBay

[Jub]

McGill motorsports...just came to me

Fuel Pressure Regulator | Carburetor fed, low pressure | Rod Ends | Bearings | Racers Hardware | McGill Motorsports

[n10]

Originally Posted by Jub

n10,

I bought mine from some place in Europe a year ago-ish, it was like Mc -something or others (took like 2 weeks to get it). But then one day I was in autozone and saw one similar on shelf. Turns out there pretty universal. They have a dial which you can set in 0.5 psi intervals.

I just briefly checked eBay and they have them there too (you want one that can be set in lower range psi 0.5-6-ish (weber carbs run best around 2-4psi):
Fuel Pressure Regulator Dune Buggy VW Baja Bug | eBay

Thanks!