I'm use to barley touching the key and vroom. My 2001 xk8 took a few cranks but after I disconnected the battery and touched positive terminal it started quickly whst a feel is Normal. The 2004 XKR always cranks a couple times but on occassion it needs a longer more extended crank. Occasionally it will studder on start taking a second or two then come up to smooth idle. I've measured the fuel pressure and its perfectly in spec. I'd really like to turn that key and instant start every time. The car has been well kept and has 49,000 miles. Your thoughts?

 

I have checked and there are no codes.

 

I would check compression as slow starting is a symptom, especially the 01 as it comes stock with a nikasil block which is linerless aluminum with a silicon coating.

 

Thank you, I thought by 2004 they had completely changed that.

 

Occasionally this symptom is a result of a defective anti drain back valve at fuel pump. The valve allows fuel to drain back and the pump must refill the system prior to start. You can check for fuel at the fitting on the driver side on the rail. remove the valve cap and press the stem. have someone turn key on. There should be fuel immediately. Any delay means it has to pump from tank to the rail. Therefore; defective anti drain back valve. 2003 fwd has a different fuel pump and canister system.

 

Thank you mine is 2004 XKR. Fuel pressure measured electronically is instantly about 53 lbs at start up. If I cycle the key fast it hits the fuel pump again and I saw it hit 70. Lol. It remains in low 50s at start up and increases going down the road at higher revs pushing it. The pressure holds tight for about 5 minutes after turning off, then bleeds down, but turn key and instantly back to 53 ish before start. Fuel pressure seems great. Tank you.

 

CRC makes a great MAF cleaner. 6 or 7 bucks. Sometimes even something simple like seating and unseating the MAF sensor a few times can kinda clean up connections and make a difference.

Unhappy plugs?

Gunky throttle body butterfly - a little air starvation for a sec?

A short pause at key turn,,, just before you HIT it, let the rail pressure up - maybe try that...?

These are such complex cars (to me) so I'm wondering what other ideas folks offer up.

 

I bought the crc maf cleaner and thoroughly sprayed it, no gunk cane off at all. I actually took it out and re-installed and while drying i checked the rest of the air flow tubing and throttle body which looked almost new. Filter is new, plugs have maybe 3,000 miles if that on them. Air cleaner looks brand new, fuel filter about 3,000 miles.
I've tried the short pause but watching the fuel pressure electronically, it hits instantly and has not made any difference if I do or don't. Thank you, all great points.

 

In the spirit of continuing with the cheap external fixes, have you tried a reputable injector cleaner? Most of us go with Techron, in the concentration listed on the bottle. Now that you have a new fuel filter, it might be a good time to add that in. Might somehow help with the injector spray pattern.

Might also be a good to double check the voltage on the fuse box post in the engine compartment as you crank. If you have an older battery or any serious resistance in the cables or junctions, high current during cranking would reduce voltage available to the control modules. Usually goes with ASC/TRAC messages.

Might also be a good time to adjust the throttle sensor. In the "bin" where the brake booster is located, check and remove any slack in the throttle cable (no tools required). Then, ignition on, engine off, exercise the throttle pedal on its entire range. Do this slowly and multiple times. This reputedly "teaches" the ECU about the throttle sensor range. Would not hurt to monitor that with an OBDII device and make sure the throttle plate actually reaches 100% with the pedal to the floor.

Best of luck, keep us posted.

 

What plugs...?