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T O P I C    R E V I E W
EdinburghJoePosted - 20 Dec 2020 : 19:06:17
Evening,

I've got a Christmas question (well, it involves a coloured light, anyway).

I'm used to the way the oil pressure light behaves on my car (96v4) - it will go out after the first time I try to start the engine (I don't mean when the starter is actually running, I mean immediately afterward). The oil pressure generated just by the starter motor turning the engine over will be anough to keep it extinguished for a few seconds after I let go of the key. I notice this because I don't use the car often and it usually takes a few goes to get the fuel through and the engine to fire.

Now I notice that the oil pressure light comes back on immediately after I release the key each time. Once the engine catches it goes out and stays out, as it should.

Apart from what I've described everything else seems fine.

What's likely to have happened here? The car is low mileage (less than 40K), I've given it yearly oil changes (20w50, last change only a few weeks ago), and there is nothing much in the way of sludge inside the rocker covers so I think the engine must be pretty clean. I checked the oil level today, full of clean new oil.

Is it likely just to be the sensor, or more serious? I have what looks like a simple pressure switch - the wire goes into what looks like a large bolt under the fuel pump.

Any advice appreciated!

Thanks,

Joe
15   L A T E S T    R E P L I E S    (Newest First)
andydeans3Posted - 06 Feb 2021 : 21:10:07
Photos of the MGB electric pump and inertia switch.
You can see the cheap Michael J Mouse pump in the picture as well. I've left it for contingency.

MGB Pump,



Inertia switch:-



1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
RhysNPosted - 27 Jan 2021 : 02:17:56
Good news Andy.
andydeans3Posted - 24 Jan 2021 : 19:52:35
Got the gear change fixed. Slackened the 2 bolts as per Melle's drawing, tried sliding the whole assembly up. Then I lost reverse, so all I have is 3rd and 4th.
Slid the whole assembly down to the limit, and hey presto!, as if by magic, all 5 gears, smooth as a nut. (Getting into 1st easier than it's ever been - it had always been a bit "snicky/fiddly" to get into 1st)

Also found my new, never been used, MGB electric fuel pump, and have fitted that today. Much quieter, it only pumps occasionally to keep the pressure up.
Much better.
Need to now fit an inertia cut off switch, so that the supply is cut off, in the event of an accident.

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
andydeans3Posted - 21 Jan 2021 : 17:51:20
Melle
It's just a pump I bought on E bay. It's a long time ago, so I can't find it on my buying history. The buying history only goes back to 2019, and it was before then.
If you go to eBay.co.uk, and search for "Automotive fuel pump", the very first item, described as "Electronic automotive fuel pump, solid state (Facet Style)", looks very similar to what I'm currently using.
I'm still looking for my new MGB pump!!!!

I'm also, as of today, having gear change issues, (no 1st and 2nd, only 3rd and 4th + reverse) so have been referring to your excellent drawing, that describes how to slacken the 2 of 1/2" bolts, to adjust the steering/gear change assembly.
That's for tomorrow!

Andy

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
mellePosted - 21 Jan 2021 : 16:51:23
Andy, what type electric pump have you used?

www.saabv4.com
GeoffCPosted - 21 Jan 2021 : 14:35:36
My electric pump on the Sonett runs all the time and I haven't had any problems with leakage or over pressurising the system. So yours should be OK, mine is mounted on the floor and is a bit noisy so insulating it as Derek suggests would be a good idea.
DerekPosted - 21 Jan 2021 : 14:34:02
Some have used the Saab, and Mini, exhaust mount cotton reels. It's pot luck, so there may be more specific reccomendations.
andydeans3Posted - 20 Jan 2021 : 12:48:11
Derek
Ah, that's very interesting.
I've just got this one bolted to the floor.
I'll see how it goes, or make one final effort to find the brand new MGB pump I've got somewhere!
Andy

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
DerekPosted - 20 Jan 2021 : 12:43:30
Some pumps run all the time and have internal valves worked by the back pressure to switch the flow on and off. They sometimes need a suitable flexi mount to dampen the noise. Matching the mount to minimise the noise sometimes not so easy.
andydeans3Posted - 19 Jan 2021 : 15:42:58
Rhys/Derek
I have always been very, very careful about putting the rod in the correct way, since I first took it out years ago. It may of course have been fitted wrongly by some previous owner. One end has a clear blue hue to it, which is the end that goes in first.
It is exactly 130 mm long.

Anyway guys thanks for all your input, I'll run her on the electric pump for a while, and see if the problem manifests itself again.
Still not sure that the pump should be chuntering all the time though. There's no sign of petrol overflowing at the carb, and looking down the throat of the carb, with the ignition on, but engine not running, doesn't show any sign of petrol coming though.
Perhaps the pump has some sort of pressure by pass? It's just a pump I bought on E bay.
I have a split new electronic MGB pump somewhere, a spare I carried on some Alpine trip years ago, but I can't find it.....

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
DerekPosted - 19 Jan 2021 : 12:11:25
Yes one end is hardened. It usually shows as a light yellowing of the end. Maybe a cm or so. Would have cost virtually nothing to harden both ends and eliminate this potential problem. Saab S&R used a longer rod and a paxolin spacer to reduce the possible problems with heat transfer from the block to the pump. If there is any sort of spacer beyond a paper gasket on the standard set-up the pump plunger won't move enough.
RhysNPosted - 19 Jan 2021 : 08:44:53
I was talking with Steve at Malbrad yesterday. He told me to have a look at the pushrod. One end is hardened and are often put in the wrong way round.
andydeans3Posted - 18 Jan 2021 : 23:01:00
Made the change over this morning.
The rod is 130 mm long. I'm wondering if the cam lobe that drives fuel pump rod is worn?
Anyway, she runs fine on the electric pump, though the pump seems to run (Clicks), constantly.
It's just a simple pump I bought on E bay.

On my MGB the electric pump only "clicks" when it's filling the system, once the system is pressurised it only pumps intermittently.
Anyway, car seems to run fine, so we'll see if I get any more fuel failures.


1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
andydeans3Posted - 17 Jan 2021 : 16:49:16
I'll remove the rod, and put the pump back on to close off the aperture.
I'll report back when I've made a few runs on the electric fuel pump
I'll also check the length of the rod.

Andy

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
RhysNPosted - 17 Jan 2021 : 15:54:39
Is it possible that your pump is sucking air somewhere? Fuel hoses not tightened off?
If you take the pump off the block without a cover plate there will be a large oil leak.

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