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Hesitant when accelerating

Eccles60

Eccles60

First Renault 4 after 40 years waiting
Messages
295
Location
Solihull, West Midlands
Hi folks. My 1986 1108cc GTL is hesitant (slightly spluttery perhaps?) under load, most noticeably when accelerating and having changed into 2nd or 3rd, and slightly less so into 4th.

It starts well from cold, idles nicely whether cold or warm and runs very well on a light throttle in top - I can bowl along at 45 - 55 mph a treat. He slows a little up inclines but that's expected.

My local Renault friendly garage suggest that the carb wants a clean out but without a gasket they are reluctant to take it apart (understandable) so have tried a bottle of stuff in the tank. After 20 or 30 miles it's no better and they did offer a second go at fixing it.

Not knowing much about the Zenith 28IF (?) carb, I wondering what the collected think the problem is. I like to be forearmed with problems and it should help them anyway.

Accelerator pump and associated gubbins (does it have one)? It has electronic, contactless, ignition, by the way.

Many thanks in anticipation.
 
Hi Eccles60, it might need a clean as your garage suggested, and you could try some carburettor cleaner sprayed into the inlet with the engine revving a bit. It just might dislodge some dirt. Remove the air cleaner to do this. Also you could try tightening the two nuts that hold the carb on, as it might be sucking air in and weakening the mixture, and have a look at the emission hoses, one might be split. There isn't an accelerator pump on the 28 IF, it's a very simple carb. Hope this helps.
 
Cornish4 said:
Hi Eccles60, it might need a clean as your garage suggested, and you could try some carburettor cleaner sprayed into the inlet with the engine revving a bit. It just might dislodge some dirt. Remove the air cleaner to do this. Also you could try tightening the two nuts that hold the carb on, as it might be sucking air in and weakening the mixture, and have a look at the emission hoses, one might be split. There isn't an accelerator pump on the 28 IF, it's a very simple carb. Hope this helps.
Click to expand...
Many thanks for that. Anything will help! Cheers.
 
Eccles60 said:
Hi folks. My 1986 1108cc GTL is hesitant (slightly spluttery perhaps?) under load, most noticeably when accelerating and having changed into 2nd or 3rd, and slightly less so into 4th.

It starts well from cold, idles nicely whether cold or warm and runs very well on a light throttle in top - I can bowl along at 45 - 55 mph a treat. He slows a little up inclines but that's expected.

My local Renault friendly garage suggest that the carb wants a clean out but without a gasket they are reluctant to take it apart (understandable) so have tried a bottle of stuff in the tank. After 20 or 30 miles it's no better and they did offer a second go at fixing it.

Not knowing much about the Zenith 28IF (?) carb, I wondering what the collected think the problem is. I like to be forearmed with problems and it should help them anyway.

Accelerator pump and associated gubbins (does it have one)? It has electronic, contactless, ignition, by the way.

Many thanks in anticipation.
Click to expand...
Eccles60 said:
Hi folks. My 1986 1108cc GTL is hesitant (slightly spluttery perhaps?) under load, most noticeably when accelerating and having changed into 2nd or 3rd, and slightly less so into 4th.

It starts well from cold, idles nicely whether cold or warm and runs very well on a light throttle in top - I can bowl along at 45 - 55 mph a treat. He slows a little up inclines but that's expected.

My local Renault friendly garage suggest that the carb wants a clean out but without a gasket they are reluctant to take it apart (understandable) so have tried a bottle of stuff in the tank. After 20 or 30 miles it's no better and they did offer a second go at fixing it.

Not knowing much about the Zenith 28IF (?) carb, I wondering what the collected think the problem is. I like to be forearmed with problems and it should help them anyway.

Accelerator pump and associated gubbins (does it have one)? It has electronic, contactless, ignition, by the way.

Many thanks in anticipation.
Click to expand...

I would definitely start by opening the crab, blowing all the jets with compressed air and clean the crab bowl. While you at it, I would also fit a new fuel filter just as a good measure. Good luck.
 
Mike Cordeiro said:
I would definitely start by opening the crab, blowing all the jets with compressed air and clean the crab bowl. While you at it, I would also fit a new fuel filter just as a good measure. Good luck.
Click to expand...
Thanks, good advice. Haven't taken a carb apart for 40 years but I'll give it a go... There's actually va good YouTube video showing the removal and dismantling (and the reverse...) of the very same carb.

The bit I'm confused about is it starts from cold a treat, idles fine cold and warm and runs at fairly wide throttles well. I think the simple carb only has an idle and main jet with no accelerator pump, so where can any blockage or partial blockage be?

What have I missed?
 
It's definitely worth making sure that this jet is clear - they often get overlooked. A bit of soft wire followed by carb cleaner works well.

20200607_145831.jpg
 
Hi Eccles, before you go to the trouble of dismantling your carb, perhaps you should first check that your timing is correct.
To me, It sounds that your timing might be slightly retarded.
To advance it, loosen the distributer and turn it a fraction anti clockwise, about 5mm should do it.
Have a look here:
 
I'd go with mojobaby first - when you push your foot down a bit, the vacuum advance unit moves back (less vacuum within the manifold) so the timing becomes less advanced (fewer degrees before Top Dead Centre) compared to when cruising. If timing is a bit retarded to start with, it could just be too much for smooth running when load comes on, and the timing retards a bit more. If you have a timing light then you can make sure. Otherwise, I agree with the carb cleaning, but this option is less intrusive :p
 
mr-reno-139 said:
late to this but I would be checking dwell reading first before anything else
very common for points gap to close up and upset smooth running
Click to expand...
It's fitted with 123 electronic ignition - which seems pointless. I will check the timing is not retarded. Presumably if the vacuum advance wasn't working it would mean the timing wouldn't be retarded automatically when I accelerate and the vacuum drops. Wouldn't I get pinking and in theory the still advanced timing would not lead to performance drop-off (as a result of retarded ignition).
Am I mad? I'll check it though; as someone said, it's less intrusive than removing and dismantling the carb.
 
AdamWilkes said:
I'd go with mojobaby first - when you push your foot down a bit, the vacuum advance unit moves back (less vacuum within the manifold) so the timing becomes less advanced (fewer degrees before Top Dead Centre) compared to when cruising. If timing is a bit retarded to start with, it could just be too much for smooth running when load comes on, and the timing retards a bit more. If you have a timing light then you can make sure. Otherwise, I agree with the carb cleaning, but this option is less intrusive :p
Click to expand...
Good idea, I'll check it. Thanks.
 
I'm beginning to think it could be retarded timing. About 25 years ago I had a 1200 Mk1 Cortina. It had a rumbling bottom end so we retarded the timing to shut it up a bit but it killed performance, until you reached cruising speed and eased off the accelerator. At that stage it seemed to smooth off and run better - presumably as the vacuum advance advanced the timing. This (having thought about it) is not unlike the behaviour of my R4 - hopefully not because of a clapped out crank etc...

I'll check the timing and that video will doubtless help!
 
Of course I didn't know you had electronic ignition at this point apologies before the interruption carry on as you were :-)
 
Having taken my 28 IF carb apart I can confirm its pretty basic inside. I got an overhaul kit from Der Franzose and it all went back together fine (had a couple of bits left over!). Didn't fix my problem, but it eliminated it from the equation.
 
mr-reno-139 said:
Of course I didn't know you had electronic ignition at this point apologies before the interruption carry on as you were :-)
Click to expand...
Don't worry Paul, of course you didn't know, I should have mentioned it in my original post. I didn't mean to be facetious in my reply to you, hopefully it didn't come over as that and no offense was taken.
 
I would never get offended don't worry I end up answering all sorts of questions and I don't always have time to read all the previous replies
 
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