Fuel pump relay melted
Discussion
Advice please. Last weekend drove S1 2.8 for 30+ miles - big smile! Stopped car, returned hour later and would not start. Noticed no whirring sound from fuel pump on turning key in ignition. Checked fuel pump relay in passenger well and found it melted. Obtained relay from local Ford dealer, inserted same and started ok. However, no whirring sound from fuel pump but got home ok. Yesterday took car out for another run Teeside to Runswick Bay - another big smile but continually checking state of fuel relay. Got home and examined relay again and found it hot and slight melting again. Clearly I don't want to be continually exchanging relays without establishing the cause. Any ideas anyone?
If it's a bad contact on the relay, the heatsource will be in the relay socket: In that case the socket will be molten too, and one ore more of the terminals will be black.
If that is not the case, the fuelpump apparently draws too much current. This could be due to a short circuit or a fault in the pump. To check this, remove the relay, remove the terminal from the pump and mesure the resistance between the wire and one of the earth points on the chassis. The resistance should be infinite. If you get any reading at all, the copper of the wire is probably rubbing against the chassis or an other wire. also if you mesure infinite resistance at this point, it's possible that a wire only shorts while driving, due to the vibrations and movements of the car. Check the wire along its entire length.
If the above desn't solve the problem, probably the pump itself has broken and draws too much amps. This is difficult to check if you don't know how much a healthy pump draws. Secondly you'll need an ammeter that shows high amps, something most ordinary meters are not capable of. In that case it's better to change the pump.
Good luck!
Ronald
If that is not the case, the fuelpump apparently draws too much current. This could be due to a short circuit or a fault in the pump. To check this, remove the relay, remove the terminal from the pump and mesure the resistance between the wire and one of the earth points on the chassis. The resistance should be infinite. If you get any reading at all, the copper of the wire is probably rubbing against the chassis or an other wire. also if you mesure infinite resistance at this point, it's possible that a wire only shorts while driving, due to the vibrations and movements of the car. Check the wire along its entire length.
If the above desn't solve the problem, probably the pump itself has broken and draws too much amps. This is difficult to check if you don't know how much a healthy pump draws. Secondly you'll need an ammeter that shows high amps, something most ordinary meters are not capable of. In that case it's better to change the pump.
Good luck!
Ronald
Sweet Thunder said:
If it's a bad contact on the relay, the heatsource will be in the relay socket: In that case the socket will be molten too, and one ore more of the terminals will be black.
If that is not the case, the fuelpump apparently draws too much current. This could be due to a short circuit or a fault in the pump. To check this, remove the relay, remove the terminal from the pump and mesure the resistance between the wire and one of the earth points on the chassis. The resistance should be infinite. If you get any reading at all, the copper of the wire is probably rubbing against the chassis or an other wire. also if you mesure infinite resistance at this point, it's possible that a wire only shorts while driving, due to the vibrations and movements of the car. Check the wire along its entire length.
If the above desn't solve the problem, probably the pump itself has broken and draws too much amps. This is difficult to check if you don't know how much a healthy pump draws. Secondly you'll need an ammeter that shows high amps, something most ordinary meters are not capable of. In that case it's better to change the pump.
Good luck!
Ronald
If that is not the case, the fuelpump apparently draws too much current. This could be due to a short circuit or a fault in the pump. To check this, remove the relay, remove the terminal from the pump and mesure the resistance between the wire and one of the earth points on the chassis. The resistance should be infinite. If you get any reading at all, the copper of the wire is probably rubbing against the chassis or an other wire. also if you mesure infinite resistance at this point, it's possible that a wire only shorts while driving, due to the vibrations and movements of the car. Check the wire along its entire length.
If the above desn't solve the problem, probably the pump itself has broken and draws too much amps. This is difficult to check if you don't know how much a healthy pump draws. Secondly you'll need an ammeter that shows high amps, something most ordinary meters are not capable of. In that case it's better to change the pump.
Good luck!
Ronald
If the fuel pump is drawing too much current, it's because some of the windings have become shorted. If this is so then the extra energy will have to go somewhere. It'll get hot. Let the pump run for a bit, and gingerly attempt to find out how hot it is.
Normal running limits will not be enough to burn your finger, but if it's damaged in this way then it will probably be capable of doing so...... If you get my drift!
Sweet Thunder said:
If it's a bad contact on the relay, the heatsource will be in the relay socket: In that case the socket will be molten too, and one ore more of the terminals will be black.
Yes but ... the heat occurs equally on both sides of the contact. The relay socket is connected to yards of thick copper wire which act as a nice heatsink, the relay isn't. The relay is likely to reach higher temperatures than the socket. You probably will see signs of heat damage on the socket though.
Yes but... if heat is generated on the terminal end of the metal strip that runs inside the relay, then the temperature on this end will not be lower then the temperature of the other end inside the relay. That's why usually the socket material melts als well as the relay if the heat is generated between the terminals (at least in my experience)
the Steve Heath bible recons that head in the relay can be caused by a blocked pipe or a dirty filter. This will cause the flow of fuel to be restricted and cause the pump to overheat the relay as its drawing more current.
Have you changed the filter recently and checked the pipes for blocks?
hope this helps?
Have you changed the filter recently and checked the pipes for blocks?
hope this helps?
May be late, but I had this loads of times with my previous S even got to the point where the carrier melted and I had the unit totally re wired. Then came along a magic fairy who told me to Zip tie in the unit tight. The unit is upside down and works loose. When it is loose is arcs. the more it works loose the more it arcs. The terminals are now burnt and so it goes on. My latest s has double zips another 110000 miles and no problems. KISS
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