My 88 3.6 is starving for fuel. It drives ok for a while then will begin starve and eventually stop. It will restart again and run ok for a bit but then stop again. I have replaced the pump and filter with no luck. I did notice there was no non return valve after the pump which I believe there suppose to be one. Could this be a problem? So I need to check the fuel pressure regulator but I am unsure where to connect a fuel pressure guage. It should be connected to the rail after the FPR but there is no way I know how to do this without drilling a hole? There is a fitting braised on the rail but it is blank and unsure why they have this. The VCM sometimes shows Fueling Failure but no codes. I believe the presure should be 35-45 psi ? Also what elso should I be looking at? CO2 sensors perhaps? coolant sensor?. Some good help would be really appreciated

 

Hi jagcoupes,

Welcome to the Jaguar Forums! It's great to have you with us. I see that you joined in 2017 but this is your first post.

Are you certain your stalling is caused by fuel starvation? Could it be caused by some other problem, such as a faulty crankshaft position sensor (CPS) or oxygen sensor (O2S) or coolant temperature sensor (CTS)? Have you checked the wiring at the CTS for damage to the wiring allowing it to short on the hood? This was a known problem on the earlier XJ40s.

Intermittent stalling can be caused by multiple components operating out of spec. How long since your last good tune-up (plugs, wires, distributor cap & rotor, air & fuel filters, gunk cleaned from the air intake plumbing, idle air control valve (IACV) cleaned, throttle position sensor (TPS) cleaned, electrical connectors and ground points in the engine bay cleaned including the engine ground strap, drive belts checked, etc.)?

The crankshaft position sensor is a common failure point that can cause intermittent stalling, hard starting and odd difficult-to-diagnose electrical gremlins, so many Jag owners replace the CPS preemptively and put the old one in the trunk/boot as an emergency spare.

There is no fuel pressure test port or Schrader valve on an XJ40. To test the fuel pressure, the gauge must be inserted between the fuel pump and fuel pressure regulator. Bryan N, one of the experts at the Jag-Lovers forum, came up with this setup for connecting between the fuel line and inlet end of the fuel rail (closest to the firewall/bulkhead):



The fuel pressure regulator (FPR) is another common failure point and if yours is original it should be replaced. But one quick check you can perform is to pull the vacuum hose, crank the engine, then look for wet fuel at the vacuum hose fitting, which indicates failure of the FPR diaphragm. This allows raw, unmetered fuel to be inhaled into the intake manifold, leading to rich running the engine control module (ECM) will struggle to adjust for based on feedback from the O2S.

The fuel check valve or non-return valve works in conjunction with the FPR to maintain pressure in the rail. On your '88, the check valve is in the fuel line just after the fuel pump. It's Part 2 in this diagram:



Also check your transmission fluid. Low fluid has been associated with stalling while slowing to stop or turn. The fluid should be checked while hot (drive for at least 15 minutes), engine running, parked on a level surface, after running the gear selector lever through each gear position and holding each position for at least 3 seconds, Then put it back in Park and check to be sure the fluid is right at the max hot line on the dipstick. Use only a good Dexron III equivalent such as Valvoline Dex/Merc (the blue bottle, not the red Maxlife bottle which has a viscosity that is too low), Mobil 1 ATF, or Redline D4 ATF.

In the meantime, please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don