My R4 keeps cutting out!

[philip mck]

Hey people,
My 68' 845cc R4 keeps cutting out on me! This normally happens after it's been running (driving) for about fifteen minutes in normal conditions.
It always starts again afterwards, after half an hour but i'd like to be able to use it for longer journeys in the nice weather.
Here's what i've tried (solved) so far!
1, When it cuts out there's always still a spark to the plugs.
2, i've fitted a new 6 volt coil and plugs and leads.
3, Fuel pressure 'upstream' of the pump is 5 psi!!!!
4, The distributer was loose in it's mount but has now been secured.
5, i've replaced all the dizzi 'low' wires.
6, I've cleaned the jets and float chamber on the solex carb.
7, The fuel filler cap is loose enough to allow the tank to breath.
8, I've cleaned the fuel filter in the tank and the carb.
It always dies in the same fashion, a few coughs and splutters and then nothing!
Any suggestions would be gratefully recieved!

Thanks
Phil

 

[malcolm]

Hi Philip and welcome to the forum.

Does the car cut out only in traffic or does it cut out regardless of conditions? If it was only in traffic I would suspect fuel vaporisation (I have a car that does that), but otherwise have you tried changing the condenser? They can sometimes short out when hot, but invariably start working again when you check the spark. From the precision of your question I'm guessing you've tried these things.

Here is a fun one - which spark plugs are you running? Plugs for modern cars are high resistance, and it's a bad plan to fit them to cars with surpressed plug leads. I fitted some fancy modern plugs by accident and it did much the same thing as you describe. Took me a week and oodles of money to figure that one out.

5psi? Is that the standard fuel pump? You do mean downstream don't you. How did you measure it? That's very much the upper range of pressure for a standard carb without overfueling issues. What colour are your plugs?

 

[Cuno]

I've had the same problem on two occasions - on one it was a clogged fuel filter, and the other was a half-broken center pin on the distributor. The distributor was almost new, so it took a while before i figured that out.

 

[philip mck]

Hi Philip and welcome to the forum.

Does the car cut out only in traffic or does it cut out regardless of conditions? If it was only in traffic I would suspect fuel vaporisation (I have a car that does that), but otherwise have you tried changing the condenser? They can sometimes short out when hot, but invariably start working again when you check the spark. From the precision of your question I'm guessing you've tried these things.

Here is a fun one - which spark plugs are you running? Plugs for modern cars are high resistance, and it's a bad plan to fit them to cars with surpressed plug leads. I fitted some fancy modern plugs by accident and it did much the same thing as you describe. Took me a week and oodles of money to figure that one out.

5psi? Is that the standard fuel pump? You do mean downstream don't you. How did you measure it? That's very much the upper range of pressure for a standard carb without overfueling issues. What colour are your plugs?

Thanks for the welcome and the replies.

It can die in any situation, doing fifty down a duel carriageway of plodding along down a country lane at thirty.
I forgot to put in the list of my solved items that i'd replaced the condensor but i do have a spare one so i'll swap them over tomorrow. I'm using new NGK plugs and leads. They do talk in the Haynes manuel about hot and cold plugs but i wasn't convinced of the relevance!
I'm not sure about the fuel pump being the original but yes i did mean downstream. i measured the pressure using a T piece and a Gunsons Low Pressure Guage.
The plugs are a nice brown normal colour! I understand that this can also be caused by running a weak mixture but i took note of some of your advice to another R4 owner about setting them mixture.
I noticed today that the Dizzie is marked A46, is this the right one for an 845cc engine? the Haynes manuel says not!
Does anyone know where i can get a new dizzie cap/ rotor arm and fuel pump? Please?

 

[angel]

Spark plugs: '68 R4s (26HP) are happy with hot plugs. The brand does not matter, but they should be equivalent to Champion L87YC, you can check it out at the shop you bought them, they normally have comparison tables.
Distributor: A46 curve is the old "linear" curve, it should fit well your engine.
Fuel filter blockage could well be the cause,check it. Also check that between the fuel pump and block is tha bakelite spacer,it does a good job of heat insulation. Speaking of fuel pumps: Early Solex carbs are very sensitive to high fuel pressure. On my '71 R4 (Solex 28 IBS carb) I had some problems with flooding. The fuel pump had been replaced with a Sofabex "sealed type" Although designed for a R4, it gave too much pressure, and the needle valve would not close. When I swapped pumps with my '75 R4 (early-style SEV-Marchal) it worked fine! Even more strange is that Zenith carbs have no problem, whichever pump you fit. So check this out, especially since fuel pressure is 5 psi (very high-normal pressure on R4s is 0,7 psi!!)

 

[philip mck]

Thanks Angel

I've replaced all the fuel line with new rubber ones! I feared that air was getting into the lines and causing fuel starvation, hence the engine cutting out. So i don't have a Bakerlite spacer, is it just a restrictor?
Do you know where i could get a SEV Marchal pump from? I've tried all my local auto factors and they don't list any parts at all! Funniest ones are the YTS kids who can't belive that cars where around that long ago!
I've been trying to get a new distributer cap from my local Renault dealer and they're saying that parts are only available in France and will take 10 days to arrive! Is this the norm?
I'll try out your ideas tomorrow and post my results .
Phil

 

[angel]

The bakelite spacer does a good job of insulating the pump from engine block heat transformation.If you cannot find it, go to a hardware store, the should have bakelite in various thicknesses. It is about 6mm thick. Then use your fuel pump gaskets as a template to make it. As for the "old style" fuel pumps (screwed together) I am afraid they have been out of production for some years, having been replaced by the sealed type. Try Ebay maybe. Renault dealers are the worst source of parts for the R4,they don't have stocks on such old vehicles and are unbelievably expensive. Where do you live? Maybe I can find you the distributor cap as we have a lot of R4 spares here...

 

[Mike from Spain]

Loads of dizzy caps on ebay and other spares too. You'll also get dizzy caps, rotor arms, points and condensers from your local motor factor. I wouldn't even step into a Renault parts dept. They completely and utterly rip you off! Sorry, ranting about Renault again!!

 

[philip mck]

Thanks for all the replies peeps.

Angel you're my hero!

On your advice that Solex carbs are sensitive to fuel pressure, mine being 5psi downstream of the pump. I construted a home made pressure restritor this morning out of a crimped peice of brake pipe and fitted it between the pump and carb. I road tested it with just a little tribulation (and a full tool kit) and thirty one miles later, the engine's never missed a beat. Not a cough, splutter or sniff. The furthest i've managed to get without breaking down previously was twelve miles! A trip to the coast this weekend is already being planned.
I can't thank you enough.
phil

 

[malcolm]

I've had a few of those impossible to solve problems over the last year. Problems where you give up and replace every part in sight and still don't get there. One before last I ended up changing the whole engine.

Respect to Angel for the long distance diagnosis.

Respect also to Philip for coming up with a test restrictor. It's ver7y much in the spirit of things to run these cars without spenging money. Hopefully you've found the answer and your trip to the coast will find you sunshine and sand .