My 86, after warm up, has severe hesitation and sometimes back fires through the intake during a hard acceleration. Sometimes, particularly under load, it has to be pulled over, and shut down for a few minutes. After resting, it seems to be OK but I'm usually very gentle with the foot feed until I get home. In PARK, the engine accelerates as if nothing is wrong.

Fuel tanks have been "in-car" flushed twice(very rusty). Injectors, fuel pump, filter and tank screens replaced.

To confirm my fuel supply is/is not the problem, would it make since to put a gauge on the fuel rail to monitor pressure at the injectors when this problem occurs? If so, how much do I want to see?

Thanks, Jim

 

Yes, a pressure gauge is a good idea. Simply disconnect the hose to the cold start injector and attach your gauge to the now-vacant nipple on the fuel rail.

You'll have to figure out how to monitor the radings while driving. I use a ong hose and tape the gauge to the windshield.

Fuel pressure s/b 36 psi when cranking and about the same when driving, with a small drop under closed throttle and a small increase as throttle opening increases.

If you get a big pressure drop when the engine misbehaves then you either have a supply problem or a pressure regulator problem.

First, though, you might wanna remove your filter and empty the contents into a clean jar. What you see/don't see might dictate your next steps. You might still have some lingering rust-in-the-fuel issues. If so, consider installing two filters (one from each tank) *before* the fuel pump. This will protect your new fuel pump.

A pal of mine had a rusty fuel issues. After cleaning the tanks best he could he installed two filters as mentioned. They clogged in a couple of days. The second pair of filters clogged after a couple weeks. The third pair clogged after a few months. The fourth pair haven't clogged at all...and that was 3-4 years ago.

Cheers
DD

 

Those are the classic clogged fuel filter symptoms. Once your tank starts to rust, that filter fills up quickly. Ask me how I know!

Doug's advice is good. Check out the contents of the fuel filter and see where you stand.

 

Maybe a dumb question,... Can I back flush the main filter and re-use? I've bought four of them.

 

You can try; I can't think fo any harm in doing so. You might be able to flush out gross crud....but not all the crud, of course. Some will remained trapped in the filtering media, as intended.

If you think (or know) that you still have a rusty fuel problem I cannot over-stress the importance of protecting your fuel pump. These pumps will last for decades under good conditions but they simply don't tolerate contaminated fuel. The factory filter is downstream of the pump. You need upstream filters.

Cheers
DD

 

Well,... Finally got back to my Jag fuel project. I replaced several factory filters and the tank strainers. Put a large bowl filter prior to the pump. Still having stall while trying to accelerate issues after driving for awhile.
I installed a "T" on the line entering the fuel rail with a pressure gauge. When cold I was getting about 30 PSI. After warm up, it dropped to about 28 PSI. Did not drive it for fear of not getting back home without the normal "wait on the side of the road" and try it again in ten minutes.
Strangely, after shutting the engine off, the fuel pressure slowly started climbing and got to about 36 PSI, where it stayed for quite while.
Any thoughts?
Thanks, Jim

 

Have you replaced the fuel pressure regulator at the end of the fuel rail ?

This is designed to blow off and return fuel to the supplying tank once the fuel rail pressure is achieved. It has a line to the inlet manifold to adjust for inlet manifold pressure. I had one seize up on me once so I got over-pressure, and fuel appeared everywhere (very dangerous !!), but the opposite can happen especially if the diaphragm is not sealing, or the spring is weak.

 

At this point you've run a bunch of crud through your pump and the diminishing pressure suggests it's time for a new pump. Be sure to add a prefilter. I use WIX 33003. It's 3/8 in and out so you'll have to fashion some sort of adapter to fit the 1/2 suppyl from the tank. If you search I recall someone else found a WIX filter with 1/2 inch in and out. I recently had to change the filters. They were full of crud. If I didnt have the pre-filters all that crud would have worn the pump vanes which is what i suspect is happening to your pump causing low pressure when hot. I'm running a stock series 3 pump that has to be at least 20 years old and it feed my 450HP SBC 408 jsut fine now. I've got a spare pump at the read but haven't had to use it yet.

 

So what we are saying is that 28-30 psi is not enough? Would it make since to relocate the pressure gauge to just after the pump to confirm it's defective or a waste of time?
Also,.... what would cause the pressure increase after shutting the engine off? Curiosity is killing me.

Thanks, Jim

 

Spec is 36 psi as mentioned earlier in post #2





You mean checking unregulated fuel pressure? Might be a good idea. The pump should put out 75psi or so, unregulated. If it isn't, there's your problem....or at least part of it. As mentioned, the crud may have hurt the pump....pretty common.

If your pump is 'putting out' OK but you still have only 28-30 psi at the fuel rail then you obviously still have problems downstream of the pump....most likely a regulator as Fraser mentioned.



Weird. I'll have to mull that over.

Cheers
DD

 

Were they clogged? Did you empty them into a clear container so you could see how much crud, if any, is still in the fuel?



Is it getting cruddy, or staying clean?

Cheers
DD

 

Removed the fuel filter bowl (prior to the pump) and fuel looked slightly rust colored but no crud. Guess the new tank strainers are doing their job. Also learned a lesson about fuel siphoning.
Right afterwards, I pulled the hose off the fuel rail (after the installed gauge) and plugged it. Obviously not gonna start but got 75 psi fuel pressure almost immediately deadheading to the gauge.
Sounds like Fraser guessed right on the regulator.
Any more thoughts prior to buying a new one?
Thanks, Jim

 

Finally got the new Beck/Arnley pressure regulator installed. The fuel pressure is about the same, 30 psi during cranking and running. The only difference I can see is it is steadier. Fluctuates slightly during throttle movement only and pressure does not climb as quickly when engine is shut off as noted in post #6. After warm-up, the pressure drops to 28 psi.

Additionally,... When I remove the vacuum line from the regulator, the fuel pressure jumps to 35+ psi and the motor smooths out allot if plugged.

New regulator junk?? Can they be adjusted some way. Could it be vacuum related?


Thoughts,...

Thx, Jim

 

This is the same thing that is happening to me, but my fuel system is clean. I did the tanks pump and filter. I've checked the filter a number of times because it seems like a lack of pressure(like a clog) but its clean. but mine is not going back to 35ish until I let it cool down for an hour or so.

 

Too many other priorities have kept me away from the Jag. Hope you're having better luck.

Jim

 

Thank you for the response. I've narrowed it down to the new aftermarket pump took a dump. I hope you get yours back up and going.

 

Finally back at it. So a new pump cured your problem?
Jim

 

Veeery interesting on two planes.


1. Seem to me that if spec is 36 PSI and the regulated PSI's range from 28 to 30 that it should run fairly well, at idle and mid throttle but fade on WOT. Other factor?
A pump that can't make close to that? Points to which FPR or pump?


2. The no run issue in my Jeep has been found. Pump failure. Just depressed the Schraeder valve witht he ignition switch in "run". A bare dribble. Should have gushed. It's spec in Jaguar range. Checked other no pump feature. No inertia switch. No OP interrupt. No fuse. Swapped in a known quality 5 pin relay. All no go.


Percussion maintenance!!! Placed the ignition switch in run and with a big rubber mallet gave the rear mounted plastic tank a few healthy whacks. In to the cabin. Cranked just a moment and fired, as it always has. Not original, GM cars use a top mounted fuel pump. Known to some as to a get home measure.


It is referred to as a module. Fuel level sensor and pump. No fix, replace. Anther good part is that son has ordered up one via his sources that won't bust the budget and has offered to put it in. I gotta admit, I'm not up to the task. Down and under!! Dropping the tank will not be easy. Lots of hoses and wires. Skid plate and trailer hitch!!! I'll get the durn near 3/4 of a tank full of gas out and up on stands or better yet, ramps.


Oh, and I work on parting corroded tricky VW plastic connectors. Coil pack swap in progress. Brittle with age and heat hasn't made them part easily!!!


Carl


Carl






Carl

 

Solution - get rid of all the Jaguar fuel tank switching stuff... use Napa Gold 3299 1/2-1/2" pre filter adapted to 5/16" hose that connects to Pollak/BWD FSV3 six port switch... use two relays to control the Jag tank switch and the valve... then it will all work properly. I use a Walbro inline pump that is gravity fed by valve... my 383 SBC maintains 40-43 PSI at the gauge on the regulator.

Other photos and the complete wiring information available.. just ask. This is the second car I have converted this way. All parts are locally available and will not need replacing (except the filters every 30K miles if your tanks are CLEAN).

 

Nice work, but how does it solve incorrect fuel pressure (if that indeed is the problem at hand)?

Cheers
DD