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Running iffy again

Niels Svane

Renault 4TL '83, 1B1 845cc engine, Ducellier diz
Messages
382
Location
Denmark
So my 4 has been plodding along with the new sports exhaust for about 150km now. It has been accelerating better and keeping at 100-105 kmh is (was) no problem.
Sadly it has now developed a new (to me) issue: After driving for 5-15 minutes it is slowly beginning to loose speed and run more and more lumpy. Pulling the choke helps and let it keep it's speed to get home on recent trips.

The petrol filter is new, and I've just put on a new petrol pump but it didn't help. Could it be dirt in the petrol tank, or do you have other suggestions? I dont really want to strip the carb once again, and I can't see that any electrical issue should be the case.

I hope you guys have some good ideas, as the car gets a bit of welding soon and then hopefully will be the daily driver again.

Niels
 
The oil looks nice and it doesn't drink any water so hopefully it's not the head gasket
 
Could it be the tank-vent? :confused:
 
It is likely the tank pick up being blocked.

Test this by running the fuel pump directly from a petrol can inside the car, then test drive the car and you'll eliminate any possible problems with the tank entirely.
 
Given the levels of ethanol now in the petrol (and probably increasing), it may be worth checking that you have good modern fuel hoses. Cohline 2240 fuel hose is impervious to the stuff and recommended by some other classic car nerds. I use it, and it's good stuff but not the cheapest. Collapsing hoses internally is a regular problem it seems - I had one of those as well :laughing: Just an idea :)
 
Weird thought, although I have had a classic car suffer with the symptoms you describe. I eventually tracked the problem down to a hair-line fracture in the body of the carburettor, which expanded a microscopic amount as the body of the carburettor warmed up, thus admitting air into the chambers and weakening the mixture enough to stall the car. As with your car, the only solution was to pull out the choke, which enriched the mixture enough to keep the car going enough to drive home. It might, therefore, be worth checking there are no air leaks on the body of the carburettor or around it.

In the case of the car in which I had the problem, the only solution was a new carburettor.
 
I blew down the petrol hose (at the pump inlet) and also down the tank vent hose, and presto; It actally ran normally again.... Typical :D
I have an in-line filter which I change every 6 months when running the car weekly, and after we switched to 10 % ethanol in the 95 octane petrol here, I switched exclusively to 100 octane with 5 % E.
It also runs better, cooler, faster and more economically on 100OCT so all is well.

A side note: The petrol level is pretty low a.t.m. so that might have triggerede some dirt to be pulled down the hose.
 
Weird thought, although I have had a classic car suffer with the symptoms you describe. I eventually tracked the problem down to a hair-line fracture in the body of the carburettor, which expanded a microscopic amount as the body of the carburettor warmed up, thus admitting air into the chambers and weakening the mixture enough to stall the car. As with your car, the only solution was to pull out the choke, which enriched the mixture enough to keep the car going enough to drive home. It might, therefore, be worth checking there are no air leaks on the body of the carburettor or around it.

In the case of the car in which I had the problem, the only solution was a new carburettor.

I have suspected the same as the carb have been constantly having issues (main jet mainly), so I suspected it might be the whole setup that would need exchanging soon. But now it seems fine as always once again .... The car was fully warm, and I drove for a good 20 minutes. I have to take another run this evening or tomorrow, and fill it up, and then I'll know if it reappears.
 
It's just waiting to get on the road
IMG_20200526_181333997_HDR.jpg
 
After a long long long evening, fixing the car in the roadside. On a hill. Getting neighbours to push. Rearranging the whole fuel supply system....I found out.....That......A danderlion seed was stuck in the jet in the bottom of the swimmer-housing........

Lo an behold: It drives perfectly now.



I laugh. On the inside.
 
Have no idea how it got in there though
Would you guys hesitate to drive it 2x 170km the next few days? I think it also need a proper shakedown, and really want to drive it more.
 
I see no reason to hesitate if you believe the problem is fixed. Though maybe give it a smaller test run before you go.
 
Went for a 20 km run today with no real issues what so ever (overflowing carb after a warm run is always present it seems though). So tomorrow the car will pass the Great Belt Bridge (all 16 km of it), 100 km of highway and a lot of b-roads, to get to a birthday party near Copenhagen. It'll be fine! :D
 
Only sporadically. The valve is one year old
 
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