Fuel system test question.

dkellogg3 · Jul 4, 2012

After initially installing test setup upstream of the pump should it take a while (90 seconds or so) to fill it. Its about 12 inches long.

Thanks!

Bondo · Jul 4, 2012

Re: Fuel system test question.

dkellogg3 said:
After initially installing test setup upstream of the pump should it take a while (90 seconds or so) to fill it. Its about 12 inches long.

Thanks!

Ayuh,... Yer set up on the wrong side of the pump....

Pressure is measured Down-stream of the pump...

Don S · Jul 4, 2012

Re: Fuel system test question.

What test are you referring to?

There are two sides of the pump, suction and pressure. Which do you mean when you say up stream?

Eric 3.7LX Alpha 1 · Jul 4, 2012

Re: Fuel system test question.

dkellogg3 said:
After initially installing test setup upstream of the pump should it take a while (90 seconds or so) to fill it. Its about 12 inches long.

Thanks!

also.. what are you trying to fill? a container? a piece of hose?

dkellogg3 · Jul 4, 2012

Re: Fuel system test question.

I'm on the suction side. I was between the tank and the fuel/water separator. I had just had the fuel intake tube out, and the threads looked a little stripped, so i was checking those connections.

@Eric. I'm filling the clear plastic tube in step 1of the testing procedure in the sticky.

@All... i have a steel pipe from the separator to the pump. I went to do the vacuum test, but stopped because i had gotten flare fittings, but it didn't look right. What fittings do i need in the vinyl tube at the stell line connectors?

Bondo · Jul 4, 2012

Re: Fuel system test question.

dkellogg3 said:
I'm on the suction side. I was betwern the tank snd the fuel/water separator. I had just had the fuel intake tube out, and the threads looked a little stripped, so i was checking those connections.

@Eric. I'm filling the clear pladtic tube in step 1of the testing procedure in the sticky.

@All... i have a steel pipe from the separator to the pump. I went to do the vacuum test, but stopped because i had gotten flare fittings, but it didn't look right. What fittings do i need in the vinyl tube at the stell line connectors?

Ayuh,.... What, exactly are We workin' on,..??

dkellogg3 · Jul 4, 2012

Re: Fuel system test question.

My bad.

1994 merc 4.3lx Alpha one gen 2
Newly installed edelbrock 1409 did not fix my low WOT issues/backfiring.

dkellogg3 · Jul 5, 2012

Re: Fuel system test question.

Just bumping this up... still lookin for an answer...

Thanks!

Eric 3.7LX Alpha 1 · Jul 5, 2012

Re: Fuel system test question.

Are you backfiring out the carb or exhaust?

dkellogg3 · Jul 5, 2012

Re: Fuel system test question.

Carb

Eric 3.7LX Alpha 1 · Jul 5, 2012

Re: Fuel system test question.

Carb backfire usually means running lean either......not enough fuel or too much timing.

Check to see what the timing is at.

A fuel pressure gauge temporary installed would tell you the pressure.You can get a short piece of 3/8" brake/fuel line from an auto parts store (with ends on both), 3 or 4' of 3/8" fuel hose, some hose clamps and a fuel pressure gauge and tee-(Sold at most auto parts stores).

Cut the new fuel line a couple of inches off each end. Remove the entire section of fuel line between the fuel pump and carb. Replace it with the new pieces and hose and gauge as a temporary setup to check the pressure.

You'll know it 5 minutes if it's within spec .between 3-7psi

dkellogg3 · Jul 5, 2012

Re: Fuel system test question.

Yup... i was starting to do the fuel system test in the sticky after checking fuel pickup for debris. Hookef clear vinyl between the tank and the fuel/water separator to check the tank snd anti siphon connections for air leaks. That's when i noticed that it took 90 +/- seconds just to fill 10 to 12 inches of 3/8" tubing.

Eric 3.7LX Alpha 1 · Jul 5, 2012

Re: Fuel system test question.

I would say no it should not, but
That test is for air bubbles only. Basically a leak in the fuel system above the fuel in the tank before the clear hose in your test.
Did you seee any bubbles?

If not, move onto the next test in the sticky, with the vac or pressure gauge, you may have a bad pump and the line won't fill quickly, as long as there were no bubbles there are no leaks there.

dkellogg3 · Jul 5, 2012

Re: Fuel system test question.

No bubbles... that goes to my next Q. I've got steel lines from the separator to the pump and from pump to carb with compression fittings. Tried theMIP barbs but didn't fit. Should i just take the compression fittings off the separator and pump and thread the barbs in directly? ...or should i get some sort of compression fitting to mate up to the barb?

ktbarrentine · Jul 5, 2012

Re: Fuel system test question.

Compression fittings or flare fittings? Typical stock setup is flare, at least mine were. I got me a flaring kit from harbor freight tools (yes, cheap, but did the trick) and made my fittings for the test rig.

dkellogg3 · Jul 5, 2012

Re: Fuel system test question.

Maybe flare. Steel line goes through brass fitting which clamps steel to the fitting at the sep. and the pump and the carb

So I've got flare fittings on my fuel equipment. What are the appropriate fittings I nrrd to be able to connect the vinyl tube to the components?i

Eric 3.7LX Alpha 1 · Jul 6, 2012

Re: Fuel system test question.

Is your separator attached directly to the engine, or bolted to the bilge/transom?

Ok for metal line from separator to fuel pump inlet if the separator is bolted to the engine directly, then it should have hose from the inlet of the separator to the tank. So as the engine moves and vibrates it won't loosen the fittings up.

Buy a small section of 3/8" fuel/brake line with the fittings attached from an auto parts store. They are sold as small as maybe 1' up to 5' I think. Cut off the ends a few inches long. Use the ends and fittings to connect to your separator, pump and carb.

Also get about 4' of 3/8" fuel hose some hose clamps you can use to attach to the small sections of the cut off lines and install the pressure gauge into.

The fuel/brake line you would buy from the auto parts store will have ends like the pic attached below, does that look like the fitting you have there?

achris · Jul 6, 2012

Re: Fuel system test question.

dkellogg3 said:
My bad.

1994 merc 4.3lx Alpha one gen 2
Newly installed edelbrock 1409 did not fix my low WOT issues/backfiring.

Check your advance curve... and DOUBLE CHECK you have a ground wire on the dissy body.... That was what my old '94 4.3LX was doing.... Took me 3 months to find the problem... You'll find a spare ground wire in the engine wiring harness right by the dissy... Swing it up and use one of the ignition module screws to connect it to the dissy....

Chris........

dkellogg3 · Jul 6, 2012

Re: Fuel system test question.

@ Eric, it's a remote filter mounted in the blige. As for the proper fittings..... I figured out that ideally I need 3/8" inverted male flare to hose bib fittings. I found some online, but I'm sure with my luck no store within a 100 mile radius will have them. As a backup I'll get the brake/fuel line you mention.

Also are the flares on these things SAE or AN/JIC? I'm assuming SAE since we're dealing with automotive stuff here, but wanted to make sure.

@Chris, I checked base timing on Sat and it was off by 4-deg (retarded), so I got that set, and it seemed to help the backfiring during cranking. How do I check the advance if the marks only go up to 12-deg advanced?

As for the ground, I think I know exactly the wire you're talking about. It its' the one I'm thinking of, it was bundled up with the purple wire I hooked up to the electric choke (I converted from divorced when I swapped carbs,

achris · Jul 6, 2012

Re: Fuel system test question.

dkellogg3 said:
...

@Chris, I checked base timing on Sat and it was off by 4-deg (retarded), so I got that set, and it seemed to help the backfiring during cranking. How do I check the advance if the marks only go up to 12-deg advanced?

....

Use an 'advance timing light'.... like this one -> http://www.ebay.com.au/itm/Digital-...t=Motors_Automotive_Tools&hash=item51a015690b

Fuel system test question.

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