Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Fuel Relay failure

Hi all,

Despite having a Tornado chip fitted to my 1997 Plus 8, 3.9 (14CUX) in May, and ignition upgrade from RPI, twice this month one of the fuel relays behind the glovebox has failed.
They were both replaced by RPI, as the wrong type was previously in situ.

A chat with a local garage suggested that the alternator voltage may be too high, but it is slightly less than 14 volts on the meter.

When the car stalled yesterday, I replaced the relay with a spare I had, but then it would not tick over and the temperature gauge doesn't work.
Is there a connection there?

If it is not over voltage, I suppose a short circuit may be the cause.
Any ideas please?

Many thanks
Phil

Hi Phil,

I anticipate that there will be people better qualified than me coming along very soon, but in the meantime, here are a few thoughts.

Having had my share of issues with 14CUX injection relays this year, it transpires that new Bosch relays of the correct type (0986AH0602) are often faulty out of the box....in my case, the car ran OK until it was warm, and then would not restart until everything had cooled down. I replaced my new one with one of the originals, and all was well again.

The other easy thing to check is as many earths as you can find - including the one on the back of the left hand cylinder head. One earth on my car was on the bulkhead immediately below the bonnet hinge, and the bulkhead paint concealed something that looked like it had been under the sea for a couple of years. I'm not sure that cleaning it all up did anything positive, although it made me feel better!

I'm not a million miles away from you, and I do have the RoverGauge software, plus some noid lights, so (after the multiple low loader trips we have made this year) I can at least claim a small amount of knowledge. Good luck with sorting this one out, and do keep us posted.

Dave

Thank you Dave, I appreciate you taking the time to post a reply.
I do have an original type relay, with an aluminium cover, but I am having the car checked out at a local garage in a week or so, so I will keep it in its box till I know it's not going to be blown by a fault.
I will definitely get onto the earths today - thanks for that.

Phil

A good starting point when replacing any relay controlled by electronics is to ensure they are diode protected. Such are usually marked accordingly or have a schematic embossed on case indicating the quench diode is fitted internally.

Phil, I had a similar problem but instant failure of both relays. The Bosch relays in Lucas boxes are rubbish, they deteriorate on the shelf so don't even buy NOS. The Factory now use Chinese made ones, ultra reliable, sorry I have no further details but I'll gladly remove one from my '95 car for reference if you wish.

Just a check point. The relay is a 'normally open' relay. The power feed comes in on pin 30, when the relay is 'on' it supplies power to two pin 87's one pin feeds the fuel pump, the other feeds the lambda sensor heaters. If an incorrect (changeover) relay is used, or if the correct relay is faulty. it may power the pump, but fail to power the lambda sensor heaters. The result will be limp home mode, bad idle, and it will feel a bit 'tom and dick'

.

Thank you again for the replies. Taff, I would be very grateful to know exactly what to buy to get a reliable relay.

Teknome, I have had both fail over the last month or so. It is definitely starting to look like it is faulty relays, but as the temp gauge stopped working last time it happened, I am having the electrics checked over at a local garage next week, just in case.

By way of an update, and a thanks for the comments and help, here is where I am with it.

It does appear that I had two faulty relays (fuel pump and EFI) which failed within weeks of installation. A local garage checked over the electrics and found no faults.
Since replacing the relays I've had no further problems, but I have one in the glovebox as a spare, just in case.

Regarding the temperature gauge, I replaced the gauge, but to no effect. I replaced the sensor in the cylinder head, which is quite a delicate operation, and the gauge reads fine now, in the top middle sector when warmed up.

Just in case anyone is wondering:
Fuel pump relay failure: No pump noise/click when ignition is switched on and the car won't start.
EFI relay failure: Sometimes runs a bit rough but more likely is a tendency to stall when on tickover.

Both are located behind the glovebox on the bulkhead.

Thanks for taking the time to update your fuel pump relay thread.... It may just be worth adding that relays can create problems even when they might seem to be operating by CLICKING when power is switched on to them.

Other than the primary mechanical action that creates the click there is the important internal switching action that controls the output task, be that supplying power to the fuel pump, cooling fan, ECU or whatever else.

If the contacts in the switching action have an issue then that can create an intermittent fault, which can make fault finding difficult, for kit can appear operational then fail, and next time you try all seems well... Thus when fault finding if the kit is operating over numerous switching actions... No fault found by the garage. Of course ECU`s evolved in time to have the ability to detect and record intermittent faults.

Many folk who have suffered relay issues now carry a spare, though as has been pointed out, off-shoring industry and counterfeiting parts has created quality issues for many a year since cutting costs became the primary objective ... ..?

The main thing is that you are sorted now and have gained a bit of understanding as to the possible issues.

Well said George, I well remember the embarrassing time I put a finger on a relay, felt it clicking and declared it sound! I carried on fault tracing the circuit and only later substituted the relay that I was convinced was fine.

Only then did I pop the relays cover and could see it was clicking for sure but it wasn’t switching. Never ASSUME as the saying goes…..

Good heads up buddy.

BR
Colin