fuel pump...maybe - 6066 (1960-1966) GMC Truck Club

mtruckr · #1 May 28th, 2013, 02:45 PM

66 305E was idling in a driveway for 5 minutes after being driven for 15 minutes... fully warm. It then died while departing. Cranked immediately with ether spray into carb. Pulled fuel line- fuel pumped out with starter spin.
Then ran okay with fuel line re-attached.

One old school thought- maybe vapor lock.
Second thought- fuel pump might be getting old.

2 weeks later (yesterday), when next run... engine starts okay, warms for 3 minutes, then dies abruptly when out of the driveway. No apparent fuel pumping out of detached fuel hose between pump and carb.

Several details- fuel filter in line between pump and carb seemed almost impossible to blow through (removed it for now). Fuel level in tank was kinda low (I'm sure it's been lower in the last 5 yrs of driving), so I added 4 or 5 gallons. Fuel did not act like it wanted to go into the filler neck... took a long time to settle (was filling without nozzle or funnel , so it was being spoon-fed from smaller containers)

Found another fuel pump in the shop (Airtex 40050, I believe)... has not been used for several years since an engine swap. Spring had lots of tension and made a sucking noise when hand-tested. Installed it- still no fuel pumping out through the fuel hose.

This process will go better when I have a second set of eyes (and smarter eyes, at that) helping. Just wanted to get input from y'all in the meantime.

Might be fuel hose issue further back.
Might be a fuel pick-up issue...

This is an old Suburban that is 'original' (old and rusty)
5 years of 10% ethanol may be taking its toll.

All input appreciated !
Kelly Ott
Alpharetta GA
'66 Suburban

FetchMeAPepsi · #2 May 28th, 2013, 06:42 PM

IM no pro but it sounds to me like you got a plugged screen in your tank. That's my guess. Pump seems to be working, it just doesnt have anything to pump out because the tank isnt giving it up.

mtruckr · #3 May 28th, 2013, 06:59 PM

Another thought is that I'm not letting it pump long enough to see if the fuel will get from the tank to the fuel pump...

I figured the fuel (if it IS in there) would be just laying along the frame rail... waiting to get back to work.

But maybe I need to shoot some ether and get the engine to run for a minute or so...give that pump a chance to get the fuel from back there.

But YES, the fuel screen is a possibility. I pulled one out of a '69 back in 2010. It had been sitting in old gas for several years, and was a gummy mess.

Foley · #4 May 29th, 2013, 02:23 AM

Without being there to have a look, two things come to mind. Crud in the tank or lines or somewhere along the fuel system. But your comment about not being able to put fuel down the filler neck. Hmmmm,,,,sounds like the vent might be clogged. Fuel tanks need a vent of some kind. A lot of time the vent is in the cap or the filler neck. If no vent, the fuel pump will suck fuel for a short time and the engine will run fine. Then the suction factor becomes too strong and the pump gives up sorta. Now the pump isn't pumping/sucking, then engine dies and the system will then slowly equalize. Then it will start up, run and do the same thing all over again. Sorta like if you put an empty coke bottle in your mouth and suck until you can't suck any more. Whewww. Bob C. in northern CA

mtruckr · #5 May 30th, 2013, 02:38 PM

What seems to be the case...

The original fuel pump doesn't move at all when the intake side is stopped up.
The second pump installed moves and acts like nothing is blocked...until you block the weep hole.

So I believe the first pump is actually okay, and the replacement one is sadly useless.

What I BELIEVE was the trouble spot was actually the fuel filter... trying to blow through it was quite difficult. The difference versus a new filter is significant.

Regardless, I had ordered a new fuel pump, so I will install it today... one less thing to think about for 5 years, let's hope. Also will install a new clear fuel filter and see if the beast comes back to life.

I added more gasoline using a full-sized funnel... no apparent hassles adding fuel, so I've taken 'vent hose' off the list of potential troubles for now.

However, please forward any observations/ opinions... ya just never know.

mtruckr · #6 May 31st, 2013, 03:07 PM

So the new fuel pump was installed... as well as the new (see-through) fuel filter. Engine cranked right up, so I'm happy with the outcome despite not REALLY knowing which item caused the problem.

But of course, now the outlet tube leaks at the pump connection, so that will require some attention. Both of my sources say NOT to use thread tape on those threads. It's remotely possible that the pipe may now have a split in it or some such... regardless, it leaked easily even after close attention was paid to the tightening of it. SIGH... it's always the last 5% of the project

And I DO believe I'm already seeing little brown specks on the new bright yellow filter material...

Thanks for the input here.

raycow · #7 June 1st, 2013, 12:05 AM

Quote:

Originally Posted by mtruckr

But of course, now the outlet tube leaks at the pump connection, so that will require some attention. Both of my sources say NOT to use thread tape on those threads.

Is it the flare connection that's leaking or the pipe threads? Tape on the flare threads is a no-no. Tape on the pipe threads is ok.

Ray

Clyde · #8 June 1st, 2013, 02:08 AM

When I received my 1961 GMC 4wd Suburban w/305 V6 it would starve for gas on a long climb, it has an electric pump mounted on the frame, if I switched it on the engine would run fine. The only pump I could get was an Airtex, this cured the problem for about 100 miles then the same thing. I put another new Airtex and it worked for a couple of weeks then the same problem. From what I can tell this is a common problem with Airtex pumps. It seems the best pumps for the V6 is a Carter if you can find one. I don't put a lot of miles on the Suburban, so this took place over a couple of years. I guess this is why a lot of folks run an electric pump also. I have an electric pump on my 1966 GMC 3/4T pick up also. Hope this helps someone out.

mtruckr · #9 June 3rd, 2013, 02:29 PM

Okay... all seems well. Problem figured out and remediated...

"Old style" compression fittings seem to involve just splaying out the tube and nuzzling it up against the conical receiver.

More recent style seems to involve folding over the splayed out tube and making almost a 2-layer ending... which bottoms out easily on an old-style conical receiver (or at least... THIS one did)

Rummaging around in those old peanut cans in the garage produced a new style tube to go with the new-style cone that was on the pump...

No leaks, runs smooth...

mtruckr · #10 June 10th, 2013, 03:30 PM

Just a few days later....

I'm offering a warning that some of you are already aware of:
These machines are talking to each other.

I know this because not 7 days after I replace a fuel pump on the '66 Suburban... the same part on the same style engine (now in a '69 c20) seems to have also gone bad.

Let's hope I can use all I learned on Project #1.
Usually these events are so far apart in time that you forget what you did 'last time this happened.'