Sorry to intrude on your forum guys. I have done the advanced searches here and the posts indicate a failing fuel pump. I just want to confirm what the issue is before dropping $475.00 on a new fuel pump.

A bit of background for those that haven't seen nor read my posts in the S Type section. I am a shade tree mechanic and have a good understanding of these vehicles, mainly the 3.0 (granny motors).

I am currently helping a fellow member out, 2003 XK8, she appears to be in really nice condition. There are a few issues that follow, if you gurus might want to help us out it would be greatly appreciated.

The owner purchased the vehicle about a month ago, 123k on the clock. The owner stated a hard start condition:

-No codes are present before or after I started wrenching. The fuel trims are in order, meaning nothing off the charts.

When running, fuel pressure is at 55.6 lbs. (according to my OBDwiz ). Unfortunately with the OBDwiz as soon as I shut off motor, the computer looses connection within a couple of seconds showing a drop in pressure to 10.2 lbs.

-Turn motor over many, many seconds (maybe about 20/30 seconds) she will fire up and runs smooth. If I turn the key to #II postion wait 2 seconds then crank, she will fire right up without the 20/30 second delay.

I pulled a couple of the old iridium plugs out to have a looksie, they appeared to be in great shape. Not knowing the history, I replaced the plugs with Bosch Iridiums #9607 gapped at .040. While changing plugs, I noticed oil in 5 of the 8 spark plug wells. I know that the cam cover gaskets need to be replaced at this point. We did not have time to replace them today. I cleaned the spark plug wells out and wiped off the oil on the COPs. Two of the eight COPs are aftermarkets.

-I pulled the fuel filter out, NO black crap came out either end. I blew through each end and my breath went right through. Unfortunately I could not track down a new filter today. I put the old filter back in.

The vehicle runs great and drives smooth, just scratching my head as to why the hard start.

Still the problem persists, ideas please?

Thank you

 

Hey .. you're allowed to wander wherever it pleases you

What type of pump is in that model year?

If it is the older type, then there are perfectly good Denso subs for under $100.

If it is the "module" type with the fuel pump sitting in a plastic "module" then the canonical reference for this is the Rev's threads. He encountered a problem with this loss of fuel pressure because of the anti-drainback check valve. When they fail, you get hard start because the fuel pressure fails to be maintained in the fuel rail.

If it starts right up after the 2 second hold, then it is not the pump itself, or the plugs. It is insufficient pressure in the rail.

The fuel pressure should still be observable with odbwiz in position two. So, if you shutdown the car and turn it back to position two, the fuel pump will come on, but then just sit and watch ... the fuel pressure should drop if there is a problem with the check valve because the fuel pump will stop running until you crank. On some cars it is possible to use OBD in position one, which is even better.

Another riskier way to see the fuel pressure after shutdown is to leave the car running and pull the fuel injector fuse. Not the fuel pump relay. When that fuse is pulled, there is no power to the injectors, but no other functions are affected. The car will still be madly trying to cycle the injectors. The problem is the pump will continue running as well.

 

Having read about the great difficulty in changing pumps, I would advise your friend to turn on, wait 2 seconds, then start.