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MG MGB Technical - Fuel Pump?????

About a week or so ago I was driving home when the engine started to lose power. It lasted about 2 sec's then came back. Then did it again for about the same length of time. I was on a slight incline, it was pouring rain, and I was running at 3,500 RPM. At first I thought it was electrical since I have HAD electrical issues in the recent past and it felt like I had no juice. The red light didn't come on and the gauges and driving lights were fine.

Then again a few days ago, also in the rain, the problem happened again a couple of times. Then last night, without any rain or moisture, it did it again only much longer. The first instance was at speed up a long steep uphill freeway section that lasted about 5-6 secs and went away on the downward side. Then it was fine going up other big inclines. Then finally on my way home it started doing it on the flat and would cut out, then come back. This went on about 3 minutes or so. Trying various things I would let up on the pedal and press again, no help there. Sometimes it would work, others not. I would drop out of overdrive to raise the rev's with no difference. The only constant I am finding now is that it is after driving it for more than say 30 minutes. But even that doesn't hold up since I drove for nearly an hour while trying to find a friends place. The only difference there was most of it was on city streets and not the freeway.

Sort of at a loss on this one. Other than the ticking noise, is there a way to determine if it is a fuel problem? Being that I am extremely short on funds, I can't take it to a shop and have them sort it out nor buy a new fuel pump to find that wasn't the problem.

Not sure if it is related, but the only other weird thing going on at the moment is my oil pressure gauge is fluctuating (not in synch with the problem) from over 50 down to 25. Oh, and lastly (I would be extremely surprised if related) my exhaust pipe is flopping a bit since the muffler strap/bracket broke. That part I am going to fix in a couple minutes.

Cheers!
-Jason
1970 mgb roadster
Jason Coolbaugh

Jason, it is very easy to check if this problem is fuel related or electrical. The next time it occurs do not dip the clutch and note the reading of the rev counter, if with the car still pushing the engine round, the rev counter is still reading then the problem is likely to be fuel related, if at that point the rev counter is reading zero then the chances are that it is an electrical fault.
Bob

Sounds like it is fuel related then. All the gauge readings look normal when it is happening. i.e. release the throttle and it behaves like it should and same with depressing the clutch. I pushed the clutch in to coast a bit and the engine kept running. I let it out and it was good for a few sec's, then problem came back.

The exhaust pipe is now secure, maybe that will take care of it.

Over a year ago my headlamps went out. I removed the stereo and the problem went away. Many months later I found that it was a coincidence since it was the turn signal/high beam switch that is bad.

Before I bought this car I was told something that I have found to be very true.

"A Honda will never need you, an English sports car always will".

Every day that there is not rain I know why I got rid of my two year old Honda. The rainy days that it is acting up I start to wonder. Forcast for the next couple days is no rain - the hard top is off.

Cheers!
-Jason
Jason Coolbaugh

It does sound a fuel pump problem. You might want to check and see that the gas tank is venting properly, so the pump doesn't have to fight against a vacuum condition in the tank. A quick check on this is to stop after a long freeway drive and see if you hear a hiss when removing the gas cap.

You could also try taking a little fine sandpaper and trying to clean up the points in the fuel pump a bit. I had a similar problem several years ago; never found a definitive answer, but between switching to a vented cap and fiddling with the points on the pump, I haven't had any problems since then.
Tom G

Hi Jason,
If it was mine I'd drive it in daytime until it faltered, then I'd switch it off immediately. If the problem was fuel starvation, there should be a shortage of petrol in the carbs. So I'd have a look to see. If I didn't want to get dirty, I'd just unplug the fuel pump wire to isolate it, then try to run the car again. If it ran OK for a reasonable length of time, I'd assume that there was already fuel in the carbs and that the pump wasn't the culprit. Very easy to do and it saves the cost of a pump job if it's not needed.
A drop of water or crud in the bottom of one carb can cause temporary starvation on that carb and give symptoms similar to what you describe.
Lastly, don't forget the coil ... it can be very unreliable as it gets older.
Rgds
Kevin
Kevin Cornford

Even if the tach is still registering it could still be HT-related, a timing light (watch the flashes) will eliminate that bar the plugs. See also 'Power Drop on Second & Thrid' (sic).
Paul Hunt

I had very similar symptoms to those you describe but was a little surprised at the cause. I believe that my problems were caused by crud in the fuel tank (rust in my case). I think the fuel lines were probably picking this up causing the pump to stall, or just get blocked for a short time.

Changing the pump was an expensive job for me (I now have 2 new ones, only 1 on the car), but changing the tank has meant that everything runs fine now.

So, dont boo too quick to blame the pump, it could be a temporary blockage (does it happen more frequently with a full or empty tank of petrol?)

Richard
Richard

Jason: I had a similar problem last autumn with my 69B, also most noticable on inclines, under power. The cause was readily detected - my add-on, NAPA see-thru fuel filter was full of black crud. How it ran under even low power demand is a mystery given the amount of trash in there, but the extra fuel flow demand for more sustained running, and the angle of the incline, brought it on.
A new NAPA Gold filter ( I dont have the number handy) did the trick. It can be trimmed to fit several fuel line diameters and is a conical paper filter housed in a clear plastic shell.
As a side note the local NAPA store also sold the fancy glass and chrome see-thru type promoted by some after market parts suppliers. When I asked to buy one they discouraged me, and rightly so. They said is was used by hot rodders to dress up the engine compartment and that the plastic mesh used for filter media wasn't fine enough for street use. On a close look I had to agree.
So, check your fuel filter (and the one inside the pump too).
Good luck.
Andy
Andrew Blackley

This thread was discussed between 22/12/2002 and 23/12/2002

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