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Pump is a NO Flow

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RAC68

RAC68

Darth Vader
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Hi All,

Hate to be on this side of the query but today was the day to change the oil and set the BJ8P1 up for dry winter driving. Cocooned in an unheated garage for the past 2 weeks, the Healey was difficult to start at 20-degrees F with 20w50. Once started, the engine ran well even though its temperature never got above 60-degreese. Halfway through my local run, the car sputtered and stopped.

Arriving home on a friend’s towrope, I checked the carburetor bowls and found little gas with very little sediment (no filters used). Pulling the gas line off the carburetor, I turned on the ignition and found a modest flow from the AUF301 fuel pump.

Following a quick air bench test, which seemed to indicate the pump working, I disassembled the lower section and found no dirt or clogs. Blowing out the lines from the pump to the tank and to the carburetors, I reinstalled the pump for a flow check. After a short period of pump ticking it came to a stop as if up to pressure, however, no flow was created.

At this point, I think the pump seems capable of pumping air but not fuel. Has anyone experienced this? Any suggestions would be appreciated.

Ray (64BJ8P1)
 
Hi Randy,

I doubt it as I had the unit’s lower section apart prior to the reinstall and last test. I didn’t take the top cover off yet as the pump ticked away when on the bench connected to a 12V battery. It seems funny that the pump moves air but seems to fail pushing fuel. I would expect the triggering electrics to either works or not and not be affected by fuel resistance.

While typing this reply, I am beginning to wonder if it could be the pump’s solenoid coil. Although, in my limited experience, I have not heard of this type of failure, I could see how a weakening solenoid could exhibit pumping air but be too weak to push fuel.

Any thoughts?
Thanks and all the best,
Ray (64BJ8P1
 
RAC68 said:
... After a short period of pump ticking it came to a stop as if up to pressure, however, no flow was created.

At this point, I think the pump seems capable of pumping air but not fuel. Has anyone experienced this? Any suggestions would be appreciated.
Click to expand...

That's a not uncommon failure mode for an SU fuel pump (hence the old trick of giving them a whack with a knockoff hammer when they stop pumping). I've had several work fine on the bench, but not pump consistently in the car.

One thing that comes to mind is the intake line could be restricted; i.e. the pump is attempting to draw in fuel but can't--and the intake line is well-sealed--so the diaphragm and points throwover mechanism don't travel far enough to break the circuit and allow the spring to push the fuel out to the carbs (and start the cycle over). When it stops, check to see if the 'solenoid' part of the pump gets warmer and warmer--if so, the points are stuck closed (don't let it stay energized and stuck for too long else you'll fry something).

A simple adjustment might do the trick if the points are in good shape. I think generally it's better to adjust the diaphragm a bit looser--say, one hole--than the manual procedure proscribes.
 
Hi Bob,

Thanks for your direction. I will be de-installing and disassembling the pump today. I follow your advice and repeat blowing air through the line leading from the pump to the tank to make sure there is no restriction on the draw side of the pump. I will also try the diaphragm adjustment you suggest.

Listening to previous tails of fuel pump problems, I always felt relatively secure as my pump had never given me any indication for concern in the past 20 years of its installation. I guess I can go to my British car club meeting and voice the most common comment heard. “If you think that’s bad, let me tell you what happened to me!!!”

Thanks again,
Ray (64BJ8P1)
 
Hi Ray, you didn't mention but is the tank original?

I had a similar problem on my BN7. It turned out to be an obstructed fuel line from the tank to the pump. When the pump is 'pulling', as from the tank to the pump, inside the tank is a screen that is meant to filter out sediment. With time that screen disintegrates. When the pump is off, sediment, well 'settles' back down to the lowest part of the tank. By blowing air into the tank from the pump you in effect do the same thing. I would suggest you drain the fuel tank (there's a plug for that purpose). Flush out the tank and retry running the engine. Good luck, let us know what you find.
 
Hi Bob/Johnny,

The tank was replaced about 10 years ago was drained during the summer. Although I am not certain, I don’t think the replacement tank has a sock over the inlet. When taking the lower end of the tank apart, the pump clean. My first thought was that the inlet (to the tank) or the outlet (to carbs) lines could be plugged. After blowing air through each line and reinstalling the pump, no fuel flowed to the carbs.

I hate to say that I was hopping for dirt….but I was. I now am hopping that the points are bad as they are replaceable and bad solenoid windings would mean death for the pump.

Thanks again and all the best,
Ray (64BJ8P1)
 
Johnny said:
Hi Ray, you didn't mention but is the tank original?

I had a similar problem on my BN7. It turned out to be an obstructed fuel line from the tank to the pump. When the pump is 'pulling', as from the tank to the pump, inside the tank is a screen that is meant to filter out sediment. With time that screen disintegrates. When the pump is off, sediment, well 'settles' back down to the lowest part of the tank. By blowing air into the tank from the pump you in effect do the same thing. I would suggest you drain the fuel tank (there's a plug for that purpose). Flush out the tank and retry running the engine. Good luck, let us know what you find.
Click to expand...
I've had a few problems with fuel delivery and one I recall being a plugged up sump screen that was cleared with an air hose and another was a blocked line between the pump and tank. That line had to be replaced. It is best to occassionally blow out ALL the fuel lines with a air hose.
Patrick
 
Hi All,

Got away from the wife and Christmas chores to work on the SU fuel pump. By the way, I was incorrect in thinking I had an AUF 301. As it turned out, I have an AUF 305 with a higher flow rate and used on MGB V8s and others. I guess, after 20-years of use, it wouldn’t be appropriate to bring this delivery error to the vender.

After taking the pump apart and finding some point damage, I decided not to just replace the points but transistorize the switch through the instructions published by Dave DuBois. According to Dave, flashover diminishes the effective point switching and, over time, will increase the draw of the pump to more than 3-amps. With the installation of a transistor, resistor, and diode at about $ 5.00, the effective switching energy across the points drops to a mere 0.4-amps.

This drop in power across the points would seem to extend point life far into the future. However, I have also found that tungsten points have a tendency to develop an insulating film when not in use for an extended period. This film would burn off with the SU’s original switching amperage but possibly not under the transistorized flow. This film can easily be cleaned with a spray of tuner cleaner after an extended period of non-use. I guess I will find out if this will be another thing to deal with, however, I can always revert to original.

After a satisfactory bench test, I installed the pump and turned the key to find an initial fuel flow from the line leading to the carburetors. But then it STOPPED. Frustrated, I hit the pump body with the ratchet and the pump started again. After buttoning everything up, the Healey started and idled for an hour. Touching the pump, I could feel the pump pulsing every so often as is normal. To verify performance, I will try the car tomorrow to make sure it starts again.

If the car starts tomorrow, I will probably consider the pump OK but I can’t say I am comfortable with a pump that did require the SU-hammer. Although I have not experienced a fuel pump problem for the past 45 years (over 20 years with this pump), I am considering installing an additional pump just in case. I am looking for recommendations on which auxiliary pump and whether to install the pump in series or parallel.

Thanks to all for your suggestions.

Ray (64BJ9P1)
 
Ray,
I installed a Facet style pump from Checker Auto as my second pump and installed it in parallel with a single pole double throw switch. The Facet is the first then my SU pump. Now if a pump quits all I do is throw the switch and the other pumps takes over. For about $35 it is worth the piece of mind. Have a good day!

John
 
Hi All,

In researching the installation of a back-up fuel pump, I am seriously considering using an Airtex E8016S (Solenoid type pump, attached filter. 30 GPH, 2.5-4.5 PSI) in series with my present SU AUF 305. Although I do think John’s parallel approach to pump backup is superior if the backup was installed in close proximity to the primary pump, it presents a more complex installation when the pumps are distant.

I was thinking of cutting the fuel line somewhere in the area of the distributor and mounting the unit on the frame. If all goes as considered, I will also wire the Airtex positive power lead in series with the primary’s positive to take advantage of the rollover disconnect I have installed and switching the grounds for pump selection.

Although I am not totally secure with having one pump moving fuel through another, it seems to be the cleanest installation approach ….if it works. I would appreciate comments on the approach and any experiences with the Airtex E8016S.

Ray (64BJ8P1)
 
I don't entirely understand the logic of fitting two fuel pumps personally now that technology has changed so much since the dodgy-SU fuel pump reputation was earned. The original SU pump's weaknesses are mostly addressed by the later electronic variety and fitting a strainer that prevents tank crud entering the pump should address the rest.

I haven't any experience with the Airtex pump but it does look a pretty neat little unit. I'd only say be aware that the item you are buying is genuine and not a knock-off copy as it looks just like the sort of thing to get bashed out somewhere in Asia and sold through semi-suspecting online retailers.

Regarding two pumps in series, the only real concern I could think of is that the pressure drop across the other pump valves doesn't drop the pressure at the carb too much. If you can blow through both pumps relatively easily then it probably won't make any difference.

Andy.
 
I use the two pump system only the second one is wrapped in the boot.I purchased a new one and had the original rebuilt. It takes ten minutes to change it out although you never need the spares you carry, only the ones you don't carry.
TH
 
Andy, I couldn't agree more!

Since everyone is so concerned about the reliability of their SU pump (yes, I've had them fail on a nearly new MGB back in the 70s too) why even bother with them?

Now, I completely understand about the concours entrant; no explanation required. You keep them looking original because you have to, to be competitive.

But for the guy that actually wants to drive his car without worry of being stranded, why?

Addding an additional fuel pump is already "not original" as well as the associated plumbing (and for those that don't realize, adding additional connections is adding to the possibility of additional fuel leaks), AND wiring (same thing: more splices, more problems) so what's the logic in sticking with an SU pump?

Personally, I'm a fan of the Facet Interupter style pumps, though they're mostly for 12VDC negative ground (this can be worked around with their rubber isolating mount kits and rubber connection hoses).

Facet cube pumps are less polarity sensitive, though most max out for about 150 horsepower.

https://www.pegasusautoracing.com/group.asp?GroupID=FACET
 
RAC68 said:
I will also wire the Airtex positive power lead in series with the primary’s positive
Click to expand...
That sounds like you'll only have 6 volts per pump if you wire them in series.

I'm with the others about using just one reliable pump. I never think about fuel pumps on any of my other cars, past or present.
 
Hi All,

I am beginning to see your point.

Just finished applying the Dave DuBois transistor upgrade to an old non-working SU pump a friend gave me some time back to scavenge the aluminum body (as a replacement for a stripped fuel port in my present pump). After applying the upgrade and adjusting the points, the solenoid and diaphragm seemed to work properly. With this solenoid in my trunk, a switch would only require removing the 5 screws holding the solenoid to the body and installing the replacement. Since the pump body is not removed, the fuel lines and body remain attached and installed in the Healey.

In the event of a pump failure (assuming an its not caused by dirt or line clog) the hardest activity will be jacking up the car and removing the wheel. The only disadvantage is it will not be a flick of a switch recovery, a major advantage in inclement weather or when dressed for a party. However, the positives are no expense and no cutting, fitting, or wiring.

All the best from the NJ Blizzard
Ray (64BJ8P1)
 
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