I have an 05 XK8 with intermittent crank no start problem? I’ve done a bunch to get to this point but still have intermittent issue. I’m a very capable car guy with tools and motivation. Need a new fried to help me figure this out. I’m actually in Fountain Hills.

 

What do you do to finally get it to start?

There is a reasonably common affliction of the 4.2 cars that the check valve in the fuel pump assembly goes bad allowing fuel to drain back to the tank when you shut the car down hot. This leads to a slow start / long cranking time and often some stumbling when it first starts up.

Has the car ever quit running while driving or this only happens on startup?

 

Hey Man... There are a good few steps to the "START" process in these cars. "Requests" and "OKs" to start... These diagrams are from the 2003 Electrical Diagram... Honestly, I don't know if the electrical system in the 2003 2004 is the exact same as the 2005.

A crappy/tired relay? Just a thought... Then,

​​​​​​This is just a possibility. There is a green wire in the wiring loom coming from the transmission to the starter relay.... It delivers a signal (12v) only if the car is in N or P and is dependent on all them other checks as well... The voltage can get corrupted at the transmission IF the seals in the transmission harness plug are leaking transmission fluid (not uncommon) into the plug set. For some, simply unplugging and cleaning the plug end and pins can solve the intermittent no start,,, or so I have heard. The plug can be found (and easily disconnected) at the middle back of the transmission on the RH side. Under the car, of course, lol... There are "images" on Google if you search 6ph26 transmission plug,,, or something like that.

If you need more images of the starter wiring OR the text detailing where things are just say and I will post what I have... And,,, sorry for the image quality - screen shots

 

Thanks for your replies. I haven’t got it started again as I left town. The CPS I put in was Standard Motor Products. I’m going to try Delphi. Jag original is a Ford sourced part I’m sure. Delphi is a good OEM supplier with real quality control.

Fuel pump was replaced and pressures are good during cranking, running, and leak down after a period of time. The car has never quit once it is running. It runs great too. Injectors rebuilt too and new battery. Remember the car sat for 3 years in hot AZ sun.

The transmission wire is a great idea. First I’ll try to start in neutral to see if I get a response then go under.

FYI this was a car I rescued from a neighbor, mice got to some wires and I fixed them. Got all codes to clear and it started. It was intermittently not starting hot or after 15 minutes. Then one day it worked perfectly all day, many stop starts, 15 min, 3 hrs, half day didn’t matter. Worked perfect then next day it cranked but no start. Also, it has an open circuit on the fuel temperature sensor so I have that part to put in. Could be that but I doubt it. Also unlikely it’s CPS. I think the transmission switch is a very plausible source of the problem.

 

Good morning, Where are you located? I'm in East Mesa, just replaced the engine in my '98. I'll give you a hand over the weekend if you still need help. I'm still learning about of cars. I'm actually working on a starting issue now. Let me know. Text me at 480-748-5283.
Sam

 

I'm sorry. I misread as NO crank issue... You can disregard my stuff

 

Update - still not quite right.
So I got back home and spent some time on the cat, one strange car for sure.
First I tried to start it, nothing.
Had the new fuel temperature sensor so put it in.
Removed all engine bay relays and tested them on the bench. All worked fine.
Did a hard reset (battery cables touched together).
Installed fuel pressure gauge.
Key on to prime line, did this 3 times to get the pressure up to about 40.
Fired right up! Unbelievable!
Drove it for about 20 minutes, runs great.
Back home and turned it off. About 1 minute later tried to restart, crank, crank, short burble for 1 sec like it might start, nothing.
Gave up for the night.

I’ll try hard reset again in the morning (first I’ll just try to start it). New, better quality CPS arrived late tonight, might just put this in. I doubt it will matter but I have it so might as well.

Anybody have any thoughts on this?

 

Here’s another bit of info. Since it didn’t start after it was running earlier today, I decided to see if there were any codes stored. Nothing in the stored codes but the pending codes showed P0335 CPS. Hmm. I have the new CPS (Delphi) to replace the currently installed new Standard Motor Products CPS.

Any thoughts on what might cause a warmed up car to set off P0335 code for the CPS? I mean when it does start it runs great, not even a hint of failure and certainly no codes.

 

I guess there are a few directions that you could go or that folks here could take you, but what is mentioned above is a really good point and worth checking. It's something that I struggled with for a while... And, a pretty simple check if you have an obd and can monitor fuel pressures.

One way is you can easily have a look at what obd readings are while the car is running, if you can get it going again. Just watch the pressures on obd - then, shut the car off and turn the key back to the ON position so the obd stays "live" (dash warning lights lit and stuff) and watch the pressures. Should stay UP, like 40+ and sloooooowly go down if at all. If they go down fast there is a clue. Second way, is that whether the car is running or not, do the priming that you mentioned above and watch what happens to FPs on obd same way. The point is the system should hold pressure.

The problem with mine was a BUM pressure release valve that lives on the TOP of the fuel pump assembly. We'll talk better about that if need be.

Also, when I hard reset (and this is just me) I'll disconnect the cables, clip them together, and turn the key to ON durning the wait time. I don't know if it actually matters or not but my thinking is that if the systems that I am trying to reset (systems that are most only active when the car is running and ignition/key is at ON) are in the ignition circuit, then the key needs to be in the on position for them to be able to drain thru ground... Anyways, just a thing.

 

To continue with the trouble shooting I did a crank voltage test today. About 10v while cranking, 12.5 static. So decided to give the battery a nice charge and guess what, it started.

The battery is only a few months old but I guess it could be weak. I’m wondering if starter draw is too high, maybe time to rebuild it. I’ve read some other posts that this could be a cause.

Also, wondering if fuel pressure sensor/regulator could be suspect. Is it truly a regulator by varying voltage or feed pressure to ECU and it controls voltage. I’m not sure exactly how it works and how the manifold vacuum to it contributes to its function. Any comments?

 

I can’t fully explain why this works, but the results speak volumes:

get a battery tender and keep it plugged into the battery whenever the car is not being used overnight or longer. This will cure many many ills these cars suffer from. Even with a good battery and adequate charging system you will find odd problems continually cropping up. It could be the age of the electrical system contributing to a generally increased resistance in critical components. I just don’t have a solid theory why a fresh battery needs a “boost” .

But installing a battery tender has eliminated all odd electrical issues in my car, and many others here have the same experience.

Using Battery tenders are an easy way to keep these cars from being a never ending headache.


Z

 

It is just a pressure sensor with a manifold reference. The fuel system is single ended, the ECU controls the duty cycle of the pump to vary the pressure. You should see 56psid +/- on the sensor, gauge pressure will be somewhat different when referenced to atmosphere.