New Fuel Pump & Rebuild Carb - No Gas in Between!

[Walk]

Hi,
I'm new to the forum and to MG's. I bought my first MG several weeks ago (79 MG. I was having problems with it not idleing and stalling. I took it to a local shop in Marrietta, GA and had the fule pump replaced (from a HP Purolator to a SU) and had the carb (Webber 2 stage DGEV 32/36) rebuilt.

I picked it up today and drove it home ( about 15 miles), it ran good and idled well at stop lights, etc. About an hour later I decided to take it for a drive, it started great and as I backed it out, it stalled. I tried several time to restart it and could not.

I had some starting fluid and tried it and it started and then died. It is not getting any gas to the carb. I checked the fuel pump and I have about 11 volts at it so I assume it is getting power. Other than a blocked line is there anything else I can check?

Thanks
Pat

 

[100DashSix]

Hm. Gently rap on the fuel pump with a hammer? That's the only thing that I've ever done to my fuel pump, as, from time to time, it fails to go "click click click click" and therefore requires a thump or two.

 

[Walk]

I did do that, but do SU's click? I haven't heard this one click at all, even when I picked it up at the shop!

 

[100DashSix]

Ah, hm. Isn't the original pump an SU? Mine would be that original type, and, after not driving the car for a few hours, when I turn the key it clicks a bit...not really audible when the car is running, though.

Sounds like it's something else, though. Something that a hammer alone won't fix? Must be serious!

I suppose I can't offer any advice.. Further than check the usual things. Maybe the points were adjusted and not tightened and have closed up? Though that wouldn't really explain why the car started with starting fluid. And if you know no fuel is getting to the carbs, well..

Someone will probably come along and offer some sage advice on what to check.

 

[Walk]

Thanks for the thoughts. I'll tinker with it over the week-end and if I don't find anything I take it back to the shop that put the pump in on Monday.

 

[DrEntropy]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

First things first, Patrick.

Find the fuel line at the carb, undo it and port it to a good SAFE container. Half-gallon milk bottles are fair. Turn th' key to the "run" position (not to "start") and see if fuel is being delivered to the container.


This is a "flow chart" of sorts, so that is a first step. If fuel is coming from the hose it should be at a rate to deliver about a pint a minute. If NO fuel or less than that flow is occurring it's the pump. If it is passin' gas then something at the carb is amiss.

We'll wait. Just be sensible about what you are doing: no sparks, no flame, no "free range" fuel, open area for the test. /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif

 

[Walk]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Thanks, I will give this a try! Should I put my cigarett out first....

 

[David_DuBois]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Pat - Go to my Fuel Delivery Troubleshooting Guide at: https://www.mgexperience.net/article/fuel-tsg.html for a guide to troubleshooting your problem. When doing DrEntropy's check, you need to have at least 2 pints in a minute. Anything less than that and you have a problem. The 11 volts at the fuel pump is bothersome to me. Check the voltage at the fuse block where all the white wires attach. The voltage should be 12.5 volts and if it is lower than that, you are dropping the voltage somewhere, be it a tired battery, a high resistance connection, etc. Be very careful about beating on the fuel pump since it is new - if you leave marks on it, you won't be able to return it if it is in fact bad. In fact, since it is a new pump, you should not have to rap it at all to get it going and if it is an all electronic pump (it may well be since you say you can't hear it, they run a bit quieter than the original points style pumps). If it is an all electronic pump, banging on it will not make it run. Following the troubleshooting guide should lead you to where the problem is.
Cheers,

 

[DrEntropy]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

<~2~ pints in a minute>

So shoot me. /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif

~Do~ use David's guide, Pat. And beating a pump using solid-state circuitry is th' same as beating a dead horse and leaving th' evidence for the forensics team. Bad plan.

 

[jlaird]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

I can not drink 2 pints a min.........for long.

 

[Walk]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Dave & All

I read your trouble shooting guide and it's great. A starting point and a finishing point and no giveing up in between...

Before I started trouble shooting again this morning, starting with the voltage to the pump. When I checked yesterday with one meter I was getting around 11 Volts at the connecter in the boot. So I rechecked that and had about the same, so I checked the lead at other end of the pump (under the car) and only had about 9 + volts there.

I had been cranking it a lot yesterday trying to get it to start, so I decided to throw on the charger for a while and then recheck the voltage. I let it charge for about 15 minutes and then decided to check the pump while I still had the charger on, as soon as I turned the key on I head my first Click from the pump!! Still on the charger, I checked the voltage and it was reading around 13 V. and the pump was still clicking.

I went to look at the fuel filter and carb in front and I was pumping gas up out of the carb like crazy. I turned off he key and disconnected the charger.

At least I know the pump was working and that there was no blockage. I dumped the gas down the carb and let it set for about 1/2 an hour. I turned the key back on and heard the click of the pump and checked the carb and everyting was as it should be.

I started the car and with cell phone in my pocket, I took it for a 5 or 6 mile drive. It ran fine and I made the round trip back home. I have checked a couple times over the last hour or so and the pump clicks when I turn the key on and does not flood the carb.

Question: do you know if there is a low voltage limit that the pump will not work at. That's the only thing I can think of.


Thank you all for all the great advise and support. I will have to keep an eye on the voltage for a while to see if it drops off, my volt meter in the car shows I am charging at about 12-13 Volts when I dirve.

Pat

 

[RonMacPherson]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

A possibility that when you were checking the voltage supply to the pump that one of the wires was not seated fully.

Where did you place ground probe when you checked the voltage to the pump? At the pump or battery or engine ground?

I recommend that you take a good look at the wiring terminal connectors to the pump, make sure they are not corroded, loose, etc. Make sure the pump ground circuit is also in good shape.

Battery voltmeter indication is just that an indication. Better(more accurate) reading would be to temporarily mount probes to either the battery or alternator/generator post while you go for a spin.With an external volt/multimeter.

Usually the voltmeter will give you a direction to troubleshoot or warning notice that the vehicle isn't charging properly.

The vehicle needs at least 12.8 volts to run and should be running with no more than 14.7 volts. Though some later vehicles do go up over 15 volts.

Sorry I can't tell you what the operating voltage of the SU pump is. Have you gone to any SU pump websites? Might find some help there. Most point activated systems require 11.5 volts, but not all do.

 

[David_DuBois]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Dave - Ron brings up some very good points. since you saw some low voltage readings at various points, it would be a very good idea to go through the connections on the white wire circuits as Ron suggests and make sure that all of them are in good shape. You should also check that all the ground connections are clean and well preserved. Go to a local electrical supply house and get some conductive, anti-corrosion surface compound, such as Kopr-Shield to put on all the ground points, under the lugs to insure a good ground connection at each one (see my Ground Point Preparation article at https://www.mgexperience.net/article/ground-point-prep.html ).

As for the voltage limits for pump operation, the original points style pumps were supposed work down to 9 volts. The times that I have tried 9 volts on any of the pumps, they would work, but not well. I have not seen a spec for the low voltage limit for the all electronic pumps. The voltage readings that you got were inside the low voltage spec, but I assume that was without the pump running. The current draw of the pump will cause that voltage to drop even further if there is a high resistance connection in the line. The new pumps have a much higher current draw than the old pumps (up to over 5 amps as compared to 3-4 amps on the older pumps), which will make any voltage drop at a high resistance connection even worse.

Ron states the following in his post:
"Battery voltmeter indication is just that an indication. Better(more accurate) reading would be to temporarily mount probes to either the battery or alternator/generator post while you go for a spin.With an external volt/multimeter.

Usually the voltmeter will give you a direction to troubleshoot or warning notice that the vehicle isn't charging properly.

The vehicle needs at least 12.8 volts to run and should be running with no more than 14.7 volts. Though some later vehicles do go up over 15 volts."

This, to me is a good reason to purchase and mount a voltmeter in the car. I did that several years ago and it is an excellent way to keep tabs on the health of the battery and charging system. I saw the voltage drop to 12 volts when the car was being driven and less than 12 volts at idle and immediately knew that something was wrong. A new alternator cured the problem before it could strand me or my wife somewhere on the road (the MGB is our primary transportation vehicle).
Cheers,

 

[Walk]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

When I tested the pump in the boot I had the probe clip on the wire to the pump and a probe on the bolt that holds the metal pump guard to the boot wall. I tried the ground in several place in the boot and got the same reading eveytime I found a good ground point.

Dave- the car came from the PO with volt meter installed under the dash. I am not sure where it is wired to, I will have to track it down. Is this what you were talking about or should I mount a volt/Ohm meter in the car?

Ron is this what you were saying was just and indicator and not a real true reading.

It (the gage)and hand held Volt meter holds pretty steady at 13.8 Volts at idle.

 

[David_DuBois]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

"the car came from the PO with volt meter installed under the dash. I am not sure where it is wired to, I will have to track it down. Is this what you were talking about..." The under dash mounted unit is what you want. Ideally the voltmeter would be connected directly to the battery, but that is not a practical place to connect it to because it would then be on all the time. I wired mine directly to the ignition switch as a place with the minimum number of connections beween the the battery and the meter and is switched off when the ignition is off.

If you don't have the head lights or any other electrical load turned on when you are reading 13.8 volts at idle, I would first take a reading right on the battery terminals with your multimeter and see what the reading is at that point at idle. I would like to see 14.5 volts at idle, but 13.8 is probably ok, particularly is the reading at the battery terminals is a bit higher.
Cheers,

 

[Walk]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

The meter goes off with the key, so it must be wired to something related to the ignition. I will track it down and check the voltage at the battery as well.


Question on the method of testing. Do I put the probs on the + & - terminals or one on the pos and one on a grounding point for best results or does it matter?

 

[David_DuBois]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

For an accurate reading of the battery voltage, take the reading at the battery terminals. You can then start going to the individual connections looking for any voltage drop.
Cheers,

 

[Walk]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Dave I took some reading this morning.

1. Car off @ the battery 12.7 Volts

2. At idle @ the Battery 13.8 Volts

3. At Idle @ the Battery with all lights and directionals on
13.4 Volts

Thanks
Pat

 

[David_DuBois]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Pat - The 12.7 on the battery looks good, the 13.8 at idle is a bit on the low side and the 13.4 with lights and directionals on looks correspondingly low. When I say low, it is lower that I would like to see on my car, but I would probably live with it and keep an eye on the alternator. As long as the voltage doesn't drop below 13 volts at idle, I think things will be ok, but the minute you start seeing the voltage going below 13 volts at idle with nothing but the ignition on you sould get concerned.
Cheers,

 

[Walk]

Re: New Fuel Pump & Rebuild Carb - No Gas in Betw

Dave
Thanks for the information. Do you suspect that the altanator is weak and maybe should be replaced?