Fuel pump noises/slight cavitation

(Douglas) #21

Interesting thought–I looked today and the pump did slide down a bit from where I put it–the sound isn’t really like a vibration though (about to attempt to post a sound byte)

(Douglas) #22

Definitely would not want that! Mine does have different size spades so that made it easy to put back together. I also take a lot of pictures of everything as I undo it in hopes that I will make it that much easier on myself later on when I’m redoing it all together!

(Douglas) #23

Hmm is there a way to upload a short video on here??

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #24

What I’m saying is: Sometimes the spade sizes are wrong. One of those spade connectors should have a + next to it. Make sure that’s actually connected to the positive power supply.

(Douglas) #25

Ahh I see what you mean–I’m quite sure I got the positive (+) spade connected to the positive. The cars is running and driving really well. No trouble at all doing neighborhood speeds (what I started out with after 2 months off the road) so I’m certainly it’s pumping in the right direction.

(Douglas) #26

Here we go–uploaded 20 seconds of my fuel pump as it currently sounds here: https://youtu.be/teofU-_G3U8 This was recorded with a warmed up to operating temperature engine idling in the driveway.

(Aristides Balanos) #27

Yes, it sounds like cavitation to me.
Had the exact same noise and it was because of the filters (XJ12 with two tanks) I had added before the pump, they were too restrictive.
Changed them with better ones and the noise went away.

So, something is restricting your flow before the pump.

(Greg) #28

I had similar noise when I had my 1/2" hose looping a foot vertical between surge tank and pump. Changing mine to a more horizontal loop, and the noise went away.

See if you can temporarily get your loop to be more horizontal, and see if it helps or not.

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #29

I find the looping ideas puzzling. When I did this, I looped the hose around underneath the battery tray and located the filter itself far to the right, under the right end of the battery. As a result, nothing in the loop was higher than the pump inlet.

Still, I can’t see any of that making any difference as long as the level in the fuel tank is higher than the loop.

I considered cutting off the bend on the pickup tube just so I could bend the hose in a different direction. If I had known about those bendy springy things, I might have gone that way. Alternatively, I could fiddle with the alignment tangs where the pickup tube fits into the surge tank.

BTW, I have a faint recollection of a TSB that replaced the pickup tube with a pickup tube that had a vent connection to it. An additional vent line was connected and teed into the vent hoses going up to the vapor separator. I seem to recall I performed this mod while I had the pickup tube out to ditch the inlet screen. Dunno how important it is since the surge tank already has a vent, but apparently Jaguar thought it was important enough to issue the TSB.

(Dzia) #30

I have a facelift 4.0 so take what I say with a grain of salt. Facelift does not have this tangle on hoses. My concern is the fighting gravity which is causing the pump to experience cavitation.

My question is, is the sump tank REALY necessary? You could put a filter between the tank and pump and eliminate that tangle. I assume the tank is there to eliminate starvation on long sweeping curves. I would think if you kept your fuellevel at 1/4 or above starvation would not be an issue.


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #31

The surge tank does add perhaps a gallon of fuel capacity.

(Greg) #32

So did Ford get rid of the Surge tank and put the fuel pump inside the main tank?

(Dzia) #33

Yes, the fuel pump is in the tank.


(Douglas) #34

If you had cut off the bend how would you have made a new barb to put the hose over?

I have seen that TSB before but I decided against implementing it as I could not see what yet another vent hose would accomplish (except for even more possible places to leak out of!) Maybe I should have gone for it but I have to say, the car is really doing great now. It was just amazing to drive today and not smell gas once the entire time!

The noise is a bit better since I filled the tank full–going to drive with it filled right up for now and may remove/adjust my new filter in time.

Even if this pump goes, I’ve got a new better one on the way now so I’m not too worried about it. Fuel pressure at the rail is good so there won’t be any concern regarding running lean. Car hit 65MPH like a champ today!

(Douglas) #35

I doubt it’s really necessary but I put it back since it was in fine shape and keeps my car closer to original.

You’re not kidding that it’s a tangle of hoses! I am glad to be on the far side of this project–on to heater core and other coolant system projects! At least they don’t smell like the gas does!

(Greg) #36

Nice job! Yeah, the smell of fuel is a distant memory for me too. Success! At least you get to drive your car :frowning:

(Douglas) #37

It is great to be behind the wheel! (though now it’s snowing hard so no more drives this weekend alas)

I took it and my key blanks to the local hardware store today.

The whole staff came out and checked it out! And they cut my blanks and even gave me a single screw they saw I was missing in the trunk–all FREE!!! That’s my kind of service. Though I’ve definitely supported that store over the years.

Sounds like you are really getting close on yours though–I’ve seen there’s a guy at British Motors in CT parting out an engine fire XJS. Think it’s an 88 or 89. Maybe you could buy or rent the ECU out of that one?? http://www.britishmotorsltd.com/

Haven’t gotten in touch with them ever before myself but I’m hoping that parting out car may have a thing or two I could use also. Good luck!

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #38

We don’t need no steeenking barbs! Just clamped it down on the smooth tube. There’s no pressure here, nothing to blow it off.

(Douglas) #39

HA! Fair enough–I can’t argue with that!

(Michael Garcia) #40

…within reason,
a pump may be strained
to the point of low fuel pressure
because of
a faulty fuel cap
not allowing air displacement…

not that this has anything to do with what you are experiencing,
yet it is true

sometimes a car wont start
especially on a cold morning
because the tank shinks
without an appropriate draw

all you have to do is
turn the gas cap
to release the pressure
tighten it
start it right up