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MG TD TF 1500 - Odd problem with SU electronic fuel pump

I put this pump in maybe 2 months ago. Actually got the car started and running with it, likely for a total of almost .5 hours. It's an electronic SU, positive ground. So I've been trouble shooting a totally dead electrical system (found a add on hidden fuse that was blown) and when I tried to restart the car, it started just fine but died quickly. I wasn't getting the 'click click'. I did have power to the pump though and as a matter of fact it was getting quite warm. It gives only a slight click when first turning things on but will not pump fuel. It's not even trying.

It did work, for quite a while so it's not like anything could be miswired, how hard is it, one wire to the post and one to ground. I'm guessing it just plain went bad.
l rutt

Try loosening the suction and discharge lines to the pump. As Dave DuBois reminded me recently the pump will not pump if either line is plugged.

Cheers,
Jim
Jim Budrow

Jim is probably right the pump sounds like it might be trying to pump against an obstuction. Check the lines and carb float chambers. Also run some fine sandpaper through the points under the pumps cover. They tend to get corroded. Finally if all else fails, chech that they diaphram is properly adjusted. It screws in and out to adjust the pressure required to open the points. The work shop manual tells you how to do this.
Russ Oakley

Larry - Either you have a clogged inlet line or the pump is not working correctly. Whatever you do, don't leave power to the pump for more than a minute at a time until you get the problem resolved. Something is causing the pump to stall in a current on condition (that is why the pump is getting hot) and leaving power to the pump will cause it to overheat very quickly. This is very unhealthy situation for any pump, but especially for an all electronic SU fuel pump (see the attached photo for what can happen to the circuit if power is left on). As Jim suggests, disconnect the inlet line of the pump and turn the ignition on and see if the pump run properly. If it does, there is a clog in the inlet line between the tank and the pump, possibly in the filter screen in the tank. If the pump still doesn't run with the inlet line disconnected, try again with the outlet line between the pump and the carburetors disconnected. If the pump still clicks once and quits, there is a problem in the pump itself that needs to be corrected (a clog in the outlet line will not harm the pump because that will cause the pump to stall in a current off condition so there is no overheating). If you find that the problem is in the pump, contact me by e-mail and I'll see if I can help you determine what the problem is. Cheers - Dave


David DuBois

Russ' advice about sand paper on the points and adjusting the diaphragm is good advice for a points style pump, but I think that he missed the part about yours being an all electronic pump. There are no points to corrode in your pump and rotating the diaphragm at all from the position it is in, will completely stop the pump from running. Cheers - Dave
David DuBois

Inlet line is open, no problems there. Outlet is as well. Pump is only 2 months old so it must have STB.

I was thinking about a backup pump anyhow so I might look for one of the small electronic jobs. I have 2 old points pumps that don't work and was going to send those off to be made as one rebuilt electronic one this fall for my backup. My car is a MKII so I have the dual fuel lines sitting there. I'd like to have 2 pumps there all plumbed in so I only had to switch power in case of emergency.

Hopefully will hear back from Burlen as this pump is only 2 months old.
l rutt

I was going to suggest that if you have two pumps (a la Mk II) that a switch be installed so that normally you run on one pump. If trouble develops you can switch to the other pump.

With two pumps running and if one fails you won't know. Then when the second fails you are plain out of luck!
Been there done that!!

Cheers,

Bob
R. K. (Bob) Jeffers

I picked up several part numbers of the little solid state pumps off the archives. Will they all work with positive ground? Seems hard to believe they will without isolation and I dont' like that idea either.

Are there legitimate options for the solid state cube pumps that work with positive grounds? If so, how do you wire them, does it not matter? I expect to run my copper line right to the pump mounted on the fire wall next to my SU. So the fact the copper line is mounted to it assures it will have a positive connection through the line itself.
l rutt

Those little electronic cubic shaped pumps usually have two wires-one red and the other black. They are not polarity sensitive as long as you connect the red to positive and the black to negative.The steel body is not connected to the internal wiring of the pump. Be careful that you get the low pressure one only. Even then I have had to sue a pressure regulator.
Sandy
conrad sanders

Larry - See the article, Back Up Fuel Pump in the SU Fuel Pump section of my web site at: http://homepages.donobi.net/sufuelpumps/ This article was written to the MGB, but will work equally well on any car. Cheers - Dave
David DuBois

Checked your article out thoroughly. I was just concerned with the polarity issue. I plan on mounting right on the fire wall in the MKII second pump mounting point. I see they can pull 12" which should be ok.

Thanks for all the input. Now if Burlen would get back with me so I can get this SU fixed under warranty I'd be happy.
l rutt

Larry - Did you purchase the pump directly from Burlen Fuel Systems? If you didn't, they probably won't do anything about the pump. You should however call the vendor that you bought it from and they should replace it for you. Let me know if you can't get the pump replaced and I think that I may be able to help you get it running. Cheers - Dave
David DuBois

This thread was discussed between 14/07/2008 and 16/07/2008

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.