Fuel Filter geting hot

Hello people, I´ve got a question: is it normal for the fuel filter getting hot ?
I don’t mean warm, I’m talking about hot.

Thanks in advance

Are you sure you are not grabbing the FUEL PUMP because you don’t tell us what mystery car you have and the external pumps look similar to filters? (later cars have the pump-in-tank)

Well I´m in the XJS forum so my mistery car is a 1986 XJS.
And I know the difference between a filter and a fuel pump.
So the filter is getting hot.
Thanks for your answer.

I’ve never heard of this, only way I could think of a fuel filter to get hot is for the actual fuel to be hot. Is the fuel pump not hot? Are the fuel lines going to/from fuel filter not hot?

And being an 86, I assume your fuel filter is the big canister one that sits in trunk behind spare tire.

Yes, it´s the filter that sits behind the spare wheel.
I will check tomorrow how hot is the pump in comparison with the filter.
Anyway , do you agree that is not good a hot fuel filter ?
And again, thanks for your interest.

Is the reason that the fuel in the tank returns hot from the motor, that they have the fuel return via that AC cooler tube on the left of the motor.
I have never felt the pump or filter after a long run in the summer but its something I must do now.

If your fuel level is low, and your a/c is not on and/or your return fuel cooler is not hooked up, yes, the fuel can get hot. The fuel cooler is there for just that purpose, to cool down return fuel from the fuel rail.

Jon

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Thanks for your comment.
I´m in the north of Spain and it´s really hot now.
I didn’t know there was a fuel cooler.
Where exactly is located ?

Where my finger is pointing in the photo:

It uses the return from the a/c evaporator to cool it.

The excess fuel pumped to the motor travels back to the tank through the heat exchange cooler and back into the tank. Without the cooler (picture) the fuel can get so hot that it causes a vapour lock if you stop and start the car after a short time. Is your air con working?

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Sorry I forgot to tell that my car is 3.6 six cylinder.
I´m afraid I don’t have this cooler.
The air con is working perfectly after I installed a Fen Air kit with a Sanden compresor.

Thanks for your comment.
My car is 3.6 six cylinder.

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Interesting. By “hot” is it fair to say it’s almost uncomfortable to touch? I would be pretty shocked if all the fuel in the tank is getting hot enough to do this. Questions/ideas:

  1. fuel pump getting hot? ( I know already asked just repeating…)
  2. floor or back panel of boot getting hot? Wondering if missing or damaged exhaust heat shield…
  3. does situation change if tank is mostly full vs mostly empty?
  4. return line from engine routed and insulated correctly? Not next to exhaust, etc.
  5. any other strange symptoms?
    Regards
    Bob

Hopefully, someone from where the 3.6 was sold can help further. North America didn’t get the 3.6, only the V12.

Thanks Bob.
Tomorrow ( now is 1:30 AM ) will check with the engine running, the pump temperature.
The floor and boot were at normal temperature.

The sequence was this:

Got to petrol station with petrol at 1/4 of the tank.
Opened the tank lid with the normal (?) ¨ hushhh ¨sound
Filled with petrol up to 3/4
Started the engine and pump began to make a strange noise.
Arrived home and removed spare wheel an pump cover under battery.
Found the filter quite hot.

Additional possibilities:
1- fuel pump failing and somehow heating fuel
2- filter clogged or other restriction is causing fuel pump to overheat and heat fuel. But it would seem like you’d be having performance issues if this was the case.

Just thinking out loud, I’ve not actually seen either of these happen on a jag.

The filter won’t care whether it is hot or not, but the fuel pump will.
The only thing keeping the fuel pump from overheating is the cold fuel circulating through it. Since you have return fuel flow of unused fuel, you want this to come back as cool as possible. If the filter, or anything downstream is partially blocking the supply of fuel, then the pump has to worker harder and generates more heat. I would also want to make sure that the returning fuel is mixed with as big a reservoir of cold fuel as possible, before being pumped back through the pump.

I am not familiar with the setup on the 6cylinder xjs, but if there is a swirl pot in the loop, then your problem may be compounded by the returning fuel only ever being mixed with a small volume of already returned hot fuel in the swirl pot, rather than a large volume of cooler unused fuel from the main tank.

I found this problem out the hard way when I converted my car to LPG/autogas. As I ran almost exclusively with the LPG because it is cheaper fuel, so petrol would simply circulate to/from the engine bay into a small swirl pot rather than via the main tank and after a two hour drive, the (unused but running) fuel pump would get hot. Eventually, after a few months, it overheated. I altered the design so returning fuel mixed with the main tank instead and the problem went away.

I would clear out any debris in the fuel tank(s), clean the pump of any debris and fit a new fuel filter as a minimum. Persistently overheating the fuel pump will lead to its seizure.

kind regards
Marek

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Thanks Marek.
I´ve made a short trip to the MOT ( 2 hrs ) and I noticed that the fuel pump and filter got hot as yesterday.
That car was unused for several months ( rear end off to change calipers and lastly to fix and regulate handbrake calipers ), so I cannot tell if the hot fuel pump issue is new, or was something coming for long time ago.

But your comments about the returning fuel line, makes me think that the previous owner deleted the canister from the emission control. I will investigate the returning line and the modifications that the previous owner made.

Thanks again Marek and the rest of lovely Jag lovers !

Wait a minute … your 3.6 looks a lot like our 4.0s … If so, then I’m thinking your fuel filter should be located behind the wheel arch of your left front wheel. :thinking:

G’day Carli1,

I don’t know whether your car has the same fuel return arrangement as my car, a 1995 V12 X305, does with all returning fuel passing through a jet pump in the surge pot in the fuel tank.

I recently replaced my fuel pumps, and in my car it’s a tank out procedure, and the jet pump was completely blocked with scale and there would have been very little flow through it. It may be that your return line is clogged.

I’ve never felt my fuel filter after a run as it is up under the rear of the car with difficult access so I don’t know whether it gets hot or not.

Cheers,
Jeff.