Dirty fuel lines/fuel tank?
 

1982 xj6 series 3


I was having problems accelerating, it idles perfectly fine in park, once I started driving if I was to try and give it a lot of gas and floor it, it would start hesitating bad. I could drive fine doing only about 20mph. I decided to change the fuel filter and fuel pump and it did seem to improve overall acceleration but the problem sort of is still there but not to the same degree. Seems like I can hit high speeds if I don't accelerate fast with no problem but as soon as I try and floor it that's when it hesitates a little bit. Spark pugs and wires are new. Does this sound like dirty fuel/clogged injector/ or a minor clog somewhere in the fuel system? Air system is nice and tight. Most times it cranks about 4-5 seconds before starting and sometimes I have to crank it twice to start it. First cold start always starts quickly while throught the day it cranks longer than normal I feel

I reckon you are fairly onto it.

If it were mine, I would disconnect the fuel supply hose at the fuel rail, extend the hose into a container.

FUEL SPILLAGE WARNING, SO COMMON SENSE PLEASE.

Trick the ignition as you have been instructed beforehand, and after 2 seconds observe the AMOUNT of fuel in that container. I would expect about 400ml, but someone will have the L/minute specs and will post them up.

At the same time observe the flow (spurt) of fuel out of that hose. Again, I would expect a decent strong flow. These pumps move some serious fuel, so once again BE CAREFUL.

The pump simply cannot supply fuel out of that hose if it does not get the fuel FROM the tank in the first place. So, that leads to a serious inspection of the supply 1/2" hoses in the boot going from the tank to the pump. Some I have had, have had work don on the fuel system, and those supply hoses have been "clamped off" to stem the fuel flow, and the inside wall of that hose collapses (old age), and even when the clamping tool is removed the hose stays collapsed on the inside, but looks perfectly OK on the outside.

Another thing to inspect is the supply and return PIPES under the car. The supply is up the RH side, and the return is on the LH side. I have seen these damaged way too many times over the years, and tyre fitting companies are the prime culprits, as they jack the car without using the jacking points, and those pipes are real close to those jacking points.

The H will restrict supply, bith pressure and flow.

The LH side restricts return of unused fuel to the tank/s, and the engine will overfuel in this situation, and "bogging down" is the usual symptom. Too much fuel is as bad as too little fuel.

I would also consider getting a fuel pressure master gauge, and "T" it into the system, and that will give a very accurate reading of teh pressure the engine is working under. Around 30psi =/- is a good pressure to work with.

Injector issues will not alter with a new filter/pump, as the blockage has not been attended to. So, if there is an improvement when these are replaced, then I doubt the injectors are the root cause of your problem.

Fuel tank venting can cause pump starvation. Simple sort, flip the cap open, go for a drive and see if anything changes.

In the RH top corner of the boot, right up in the corner in front of the spare wheel, is the fuel distribution block, and it contains the non-return valve, and that valve can jam.