So this seems very strange to me. Whenever I put gas in my tanks (usually only fill each tank half way) the car runs great for about 20min and then starts sputtering and stalling under load but will rev in park just fine. After I limp the car home, I will usually let it sit overnight. The next time I drive, the car does not have a problem at all. This has now happened to me on 3 separate consecutive occasions. The latest being today.

I changed the fuel filter yesterday thinking I may be picking up debris. When I back flushed the old filter to see if particles were being picked up, there was not a single speck.

Any ideas?

 

Secundary filter under the hood? Don't know if all series 3's have that option.

 

I will have to look into that. I wasn't aware that there may be another fuel filter.

 

There is only one filter on the Series 3 cars (after the 1980 model) beside the spare wheel. But there is a cap/thimble filter on the pickup tube in each tank. I suppose that you might have some clogging there; first, why do you not fill the tanks? That seems odd to me but I get nervous with tanks that run low. If you have sediment in your tanks (rust flakes are a major issue with these metal tanks particularly if they are NOT REGULARLY FILLED - condensation + metal = rust) then this may be stirred up by partial filling, and then picked up on the outside of the thimble filter, thus obstructing flow under high demand. But overnight that sediment may settle away from the filter, resulting in normal performance until the cycle is repeated.

 

There is a very fine gauze filter at the bottom of each tank where the pick-up pipe is located. It is behind the large black plug on each of the 1/4 panels below the rear side bumpers. There is a large hexagon to unscrew it, the small one in the middle is a plug for draining the tank.

 

Just guessing at possibilities.

- next time it happens try switching tanks to see if the behaviour is same in both tanks. That will eliminate pickups, and the changeover valve if the same.

- tired/intermittent fuel pump

- mixture not changing from rich start after its warmed up

I had a similar problem with a carb car, and the issue was at a small mesh filter in the carb rather than at the filter. That is similar to what Gregory is talking about, in that changing the filter didnt resolve the problem.

Also wondering about the half fill thing. Do the tanks leak if you fill them?

 

Thanks for all the help! Changing tanks makes no difference. The reason I only fill them halfway is that they will leak all the way full.

 

Looking at what I wrote I think my previous logic is a flawed. Having the symptoms the same on both tanks just means you cant point the finger at an individual tank. It still leaves the possibility that both tanks have a problem or the changeover valve is blocked at the exit.

If both tanks have eroded to the point of leaking I think rectifying that as Gregory and Fraser have pointed out needs to be done as a first step. Cleaning it out may get things working but it really sounds like new tanks and related plumbing are going to be needed.

 

A shot in the dark.


Inoperative vents. Your car has a complex venting system including a charcoal filled canister behind the right head lamp.


If the caps fit really tight, and that is a stretch, a vacuum will be created as fuel is used. Strong enough to over come the pump. I don't know. The feed from the tans to the pump is gravity only.
electric pumps are great pushers, but not so good as pullers.


Test: open a cap and run. any difference? While you are at it, look and see if the FPR is returning fuel. it should No return could mean a lot of things, none good.


Off to the outside chores, Rain promised, no sign yet.


IC weed whacker quit. Ugh, have to fix the tools to do the work???
May go to the slower but lighter electric one. It's weakness is an interminable appetite for the blue colored line!!! Only two spools left... I refill my own frombulk, but t is exhausted.


Carl


Carl.

 

Whacker 'fixed". didn't like my home brew fuel blend. Picky, picky!
Drained. Added it to the lawn mower. it less picky, but some picky???


store bought 40-1 in Whacker. Fired up. flood 'em with rime and cholke, then off choke and pull til it clears and fires.


Whacked a good patch. til the thatch wrapped around the shaft and engine loaded up. More in a day or so.


got one of my battery hound cameras to work. Post stuff, mebbe.


Lunch coming up. My 1/2 day is about done.


Carl

 

You say that the tanks leak if filled more than halfway.
There, you have given the answer. You have perforations in the seams of the tanks because the tanks have been left for long periods less than full and the result is RUST, and the result of that will be rust particles at the bottom of the tank and the result of that will be debris-laden fuel when you do put fuel in and the result of that will be debris sucked up to the thimble filter at the end of the pickup tube and the result of that will be very poor performance until the debris settles away from the filter overnight. phew!
Moral: keep the tanks as full as possible on a regular basis (too late in your case). Solution: remove the plug and drain bolt at the bottom of the tank and flush debris out. Better solution: put in new tanks ( they are available but not cheap)....and replace all the filters.

 

Thanks for all the help. I bought the car a few months ago so I inherited the leaky tank. Looks like I will need to fix it right and that will involve those expensive tanks. When I have it all apart I am sure I will notice a lot of rust..... Everywhere.

She is just to pretty to not fix

 

Yep, well worth the effort by the look of it.

 

I vote for the Coolant Temp Sensor, nothing to do with fuel or filters.

 

Pretty Kitty!!
(';')

 

Very nice.


Well worth the sweat and bucks to fix her correctly.


And, might get some good news. Minor fixables found on removal.
filler neck, vent line, return line, pin hoes only, etc.


Carl

 

That fits the problem description Jose? I didnt think of it as I dont have one :-) at least not on the Jag. On the other car I replaced temp/cps and O2 at the start so never had a problem. Would be a simpler fix if it works and maybe allow the fuel tank can to be kicked down the road a bit.

How do you test? warm it up and earth it?

 

The 'could be' list is a little long.

I agree with the others that the in-tank screens being clogged is a plausible explanation and must be checked. What you find will dictate your next steps.

The coolant temp sensor...though not my choice as a likely culprit given the symptom.... can be checked with an ohm meter. We can give the specs if you wanna try it. Lacking that, simply unplug it and jump the terminals in the connector with a paper clip. This bypass will give the ECU a constant 'fully warmed up' reading. A cold engine might not like this trick so wait till the engine warm up then try it. Then, simply drive the car and see if the problem goes away. It sounds like it might take a few drive cycles for the experiment to be conclusive.

The ignition coil and module are both known to give trouble after absorbing enough engine heat. This would typically occur after much more than just 20 minutes of driving...but that isn't carved in stone.

Does your car has a ballast resistor attached directly to the coil "+" post? Some do, some don't. If so, remove it and connect the white ignition feed wire to the "+" post instead. See if anything changes. If this fixes the problem then most of us would just toss the ballast into the trash bin.

Fixing these types of problems are often 'process of elimination' situations.

Cheers
DD

 

So I recently just installed a new coolant temp sensor a couple weeks ago. No difference.

The ballast was removed prior to me owning it. I also replaced the coil when I bought it.

I would think the hesitation would happen all the time if it had to do with engine heat. Currently it only occurs about 20 min after fueling.

 

What coil did you use? It doesn't need to be anything special but it does need to be about 1.0 ohm primary resistance. There are some recent (and not so recent) discussions on this. Search "DLB102". That should get you in the right direction


No, because it takes time for the suspect components to absorb enough heat to begin failing. As mentioned this would usually be more than 20 minutes but, still, it is something to consider. In any case, failures don't *always* occur in the manner we expect them to occur

Cheers
DD