Fuel pump power supply woes - solved, thrice. (was MFRU - multi-function relay Reverse Power Protection)

[anthonym]

p.s. about six hours in to today's travels, after a couple of hours previously, the fuel pump carrier screws, six of them, had become untight (!!) despite being tight when I refitted them, so I had a petrol leak. Fixed using cross head on a small socket ratchet as the only thing that would fit in the space, accessed from underneath, could not get to the top two, but the leak seems stopped for now. 

I am thinking that replacing these with allen key headed screws (what's the correct name?) would make this a whole lot easier, access is very difficult, except for the one I had replaced as described, because I hacksawed off the screw head.

[EEK]

Relief it is not a warranty claim over the soldered joints! 

I do think it might have been the problem all along as the joint removed at the front did look OK, but looking and being are of course different things. 

Pump replacement bolts want to be about 2mm shorter so they don't bottom out at the end of the rivenut which I think there is a risk of doing. Looking at mine there is the fiber washer, a flat washer and a spring washer, also they are allen heads, assuming same length then think washers will give the required length reduction and spring washer should help with them working loose.

 

[Wrightpayne]

I keep saying its in the loom down from the inertia switch!!

[anthonym]

Good morning :-)

@EEK nice to "see" you and very many thanks for your tenacious unlimited assistance, plus a good blat and coke.

Yes that "looking ok" was why we left it in place originally, fatally, but the probe tool told no lies, 12v one side of the joint, zero the other. Red and Green. And the car worked. Same again last night, 12v one end, nothing the other. Jumped the connection and the car works. I suppose there being multiple problems in the circuit is not strange. I wonder if solving each problem leads to the creation of the next somehow.

@Wrightpayne , thanks for hanging in there :-) This time it's between the fuse and the MFRU, which of course is down in the loom from the inertia switch - but not where I think you mean, which area is one I am quietly dreading because that means replacing the wire that goes down the tunnel - yes?

edit: I found your original comment: 

I had a problem with power to the fuel pump straight away after build (1600 eu2 K). There is a crimp join in the loom where it goes into the fluted sheath. I dont know exactly where it is as caterham midlands fixed it. If you find no 12v coming into the MFRU I'd work back from the plug into the loom.

THAT sounds VERY like the joint we just replaced, a few days ago. Originally it was a crimped connection in the loom where the power came out (wire goes in, same thing) of the loom to supply the MFRU, originally it was hidden in the loom if I recall correctly. First the wire was suspect so replaced with a fused connection direct to the battery, but still using one side of that connection, so the MFRU receives clean fused power. Now cut out that crimped spade connection completely. Comment #22 in that old thread I say the same thing.

 

Any suggestions best way to insert fused direct connection from MFRU to Inertia switch? Can one replace the wire into the MFRU ? (meaning how?) It's a bit ragged after so much testing and splicing. I'll do a search. Ho ho, found the first time I had this trouble https://www.lotus7.club/forum/techtalk/car-wont-start-solved-pump-no-feed-part-number-eu2-mfru-ybw10022-eu3-ends-970

I suspect one way or another I will end up replacing the whole pump power circuit.

Anthony

[Jonathan Kay]

Sorry you're still not fixed.

...allen key headed screws (what's the correct name?)

I'd go for "hex socket head screw" and then "cheese", "dome", "button" etc within that. But no-one's going to misunderstand "Allen", although he was a real person and deserves a capital letter. On the other hand de minimis non curat hex.

Jonathan

[anthonym]

Pic of new fused connection direct from MFRU to Inertia switch, fused, cutting out yards of loom wire that is cut somewhere between the MFRU and the fuse box. This also cuts out the same number of yards of loom wire returning from the fuse box to the inertia switch. The only remaining long loom link is now from the inertia switch to the pump. I will replace this when it is convenient. 

That leaves the Earth from the pump which does NOT go to the chassis; need to trace it for future reference as poor Earth will be the remaining potential for failure, unless I also replace it when doing the 12v supply wire. Need to discover where it goes; maybe the wiring diagram will tell me.

Anthony

[anthonym]

@jk direct phone upload worked nicely. BUT i can’t “pinch zoom” (i.e expand ) the pic when viewing it which is rather important for our stuff or is that just on my phone? 

[Jonathan Kay]

Is that viewing the image while you're managing the upload or after it's uploaded to BlatChat?

Jonathan

[anthonym]

AND : again won't start. Really? Yes. This time one of the connections to the inertia switch fell apart in my hand when I touched it. It seems all the testing is itself having a deleterious impact. The wires that pulled (fell) out of the inertia switch looked "old". I've ordered a new inertia switch and in the meantime cut it from the circuit, which is getting shorter and shorter. 

I think age is the real problem, it all just needs replacing. Preferably with new wire really. The MFRU is new and works fine, indeed the old one also worked fine. Tough little units those. 

Anthony

[anthonym]

@JK it went sideways upon upload. IOS . AFTER upload.

[Jonathan Kay]

That's been reported once before. I couldn't reproduce it and don't know a fix.

Jonathan

[anthonym]

can we as users access and modify the upload afterwards?

[Jonathan Kay]

Select the image and then click this icon:

The tools are there but I can't use them to make changes consistently.

Jonathan

[rj]

Anthony has had a lot of issues with his fuel pump supply lately.

One of the issues has been that the the wiring to the inertia switch has been fried.

The fuel pump is actually one of the most power draining items in a K-powered car.

For any future re-looming of a such car I would suggest that the inertia switch with it's small terminals is moved to the coil side of the fuel pump relay so that it cuts the power to the coil rather than to the pump. The outcome will be the same: The fuel pump stops.

 

[Wrightpayne]

Working on the car yesterday, re attaching the wiring after putting the engine back in, I undid a bit of scraggy tape on the wires going to the inertia switch and I think I've uncovered the joint I mentioned earlier in the thread. The reasons I believe this the repaired 'crimped' joint are a) the two yellow / green wires joined are slightly different sizes and b) the tape coming unravelled. 
 

The bit to look at, and give a potential fault search point is the black tape with yellow / green wires either side. This tail connects to the inertia switch on the scuttle bulkhead. The joint is very close to the thick main loom.