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Goodmorning!
My 88 Jaguar XJ6 VDP has not been starting after driving any duration of time, I’ve had to wait around 20 minutes for it to start again. Additionally, it just died while driving and again will not start. Has anyone had this problem?
You need to check a few things
1st - while cranking, does the tach register about 200 rpm? If not, suspect crank position sensor
2nd - can you hear the fuel pump when turning ignition on? You can try banging on the fuel tank with your hand to see if it starts, otherwise you'll need check fuel pump operation and see if you're getting fuel pressure.
Let us know what you find and we can move from there...
You can try banging on the fuel tank with your hand to see if it starts, otherwise you'll need check fuel pump operation and see if you're getting fuel pressure.
Hi - I think the 88MY has an external fuel pump ...so tank-bang technique, while fun, may not be effective in this case?
Larry is right, an '88 XJ40 has an external fuel pump mounted on the rear suspension subframe on the left side.
On an XJ40, hard starting when hot can be caused by a number of issues:
1. Failure of the fuel pressure regulator (FPR), often in conjunction with failure of the fuel check valve. The FPR is mounted below the forward end of the fuel rail. A simple test is to remove the vacuum hose from the port on the FPR, crank then engine briefly, then check for wet fuel in the vacuum hose port, indicating the diaphragm in the FPR has failed, allowing raw unmetered fuel to be inhaled into the intake manifold causing rich running that the engine control module (ECM) cannot fully correct. Even if the diaphram has not ruptured, the FPR may no longer be holding sufficient pressure in the rail. When the fuel pump shuts off, the sudden loss of pressure allows fuel in the rail to boil/vaporize, leading to classic vapor lock. Until the vapor cools and condenses back to liquid, the vaporized fuel that makes its way through the injectors is too diluted by incoming air to combust, so the engine can't start. The FPR works with the fuel check valve to maintain proper pressure in the rail. The check valve on your '88 is in the fuel line at the inlet of the fuel pump.
2. You don't tell us your general location, but another cause of stalling and hard starting when hot is the external fuel pump overheating and/or fuel vaporizing at the fuel pump inlet. Jaguar's solution was to add a second fuel pump in parallel to the original one.
3. A clogged air filter can contribute to hard starting when hot.
4. Corrosion on battery power connections can contribute to hard starting when hot. The critical connections are the battery cable terminals, the negative battery cable ground point on the body, the connections at the alternator and starter, and both ends of the engine ground strap.
5. Another possible cause of hard starting when hot and stalling at idle is the carbon/charcoal canister purge valve sticking open, allowing fuel vapors to enter the intake manifold at idle, causing rich running that the ECM may not be able to correct.
It is also possible that your hard starting while hot and stalling issues are not directly related. One known cause of stalling when slowing down to stop or make a turn is low transmission fluid, so it would be worth checking that.
I proceeded to check all battery connections and the Fuel pressure regulator test like recommended and all seem in functional order. I let the car idle for 20 minutes, shut it off and again it will not start. It seems to be running a little rough. The Air filter looks brand new. I cannot hear any noise from the fuel pump when I stick my head under the car after turning the key into the on position and the tach bounces off of zero when turning over but may be an erroneous tachometer.
I proceeded to check all battery connections and the Fuel pressure regulator test like recommended and all seem in functional order. I let the car idle for 20 minutes, shut it off and again it will not start. It seems to be running a little rough. The Air filter looks brand new. I cannot hear any noise from the fuel pump when I stick my head under the car after turning the key into the on position and the tach bounces off of zero when turning over but may be an erroneous tachometer.
Hi 88JaguarXJ6,
Did you just visually check all the battery connections or did you remove the nuts and wire terminals from the threaded studs and clean them with a small wire brush and zero-residue electrical contact cleaner, allow the parts to dry, then reconnect the terminals and washers and snug the nuts tight but not too tight?
Regarding the FPR, the test I mentioned is just the most obvious way to detect failure of the diaphragm. But the diaphragm doesn't have to rupture for the FPR to lose its ability to hold proper pressure in the fuel rail. The next step would be to connect a fuel pressure gauge, preferably at the junction of the inlet hose and fuel rail, but this requires special (metric) pipe fittings.
The fact that the car will start when cold indicates the fuel pump is generally working, unless for some reason it is overheating and either dying or fuel is vaporizing at its inlet. The pump will only run for a second or two when the key is turned to ON to pressurize the fuel rail. On your '88 the pump is mounted on the top of the rear suspension subframe on the left side.
When you say the tach "bounces off of zero," do you mean it moves up and down, or does it hover around 200 rpm while cranking?
How long has it been since the car had a good tuneup (plugs & wires, fuel filter, distributor cap & rotor, clean the sludge out of the air intake and crankcase breather plumbing, flush the inside of the TPS body and its electrical connector, clean the EGR port on the underside of the intake manifold behind the throttle body, clean all the ground points in the engine bay, including the two on intake manifold studs and the one on the firewall/bulkhead behind the cylinder head (along with the air filter and cleaning the battery power connections and grounds that I mentioned earlier)?
What is the climate like where you live? Hot? Mild? Cold?
I indeed only performed a visual inspection and there was no evidence of corrosion. The vehicle will not start at all currently for unknown reasons so the fuel pump is still a viable reason for the issue. And bouncing off zero, i mean just barely leaving the zero mark and then returning repeatedly. And I’m sure it has been a very long time since an in depth tune up. I purchased the car around November with 75,000 miles on it, it’s sits at 80,000 now and was driving flawlessly until lately. I live in Arkansas, U.S. it’s around 30-55 degrees F on average this time of year
I indeed only performed a visual inspection and there was no evidence of corrosion. The vehicle will not start at all currently for unknown reasons so the fuel pump is still a viable reason for the issue. And bouncing off zero, i mean just barely leaving the zero mark and then returning repeatedly. And I’m sure it has been a very long time since an in depth tune up. I purchased the car around November with 75,000 miles on it, it’s sits at 80,000 now and was driving flawlessly until lately. I live in Arkansas, U.S. it’s around 30-55 degrees F on average this time of year
You really can't determine the condition of electrical connections from visual inspection. It only takes a thin layer of oxidation on terminals to add enough resistance to cause poor performance, and resistance at each connection is cumulative - it all adds up. Corrosion on these terminals tends to be a white powdery substance (lead oxide, aluminum oxide) rather than red rust (iron oxide/iron oxide-hydroxide).
One thing to be aware of is that if the voltage while cranking falls much below 11V at the ECM, the ECM will not trigger the ignition to fire, and this is one of the most common causes of Jaguar cranks-but-won't-start conditions.
The behavior of the tachometer needle may be telling you the crankshaft position sensor (CPS) is failing. Many of us have purchased a new CPS just to rule it out, and if we determine the old CPS was not the cause of the no-start, we put it in the trunk as a spare for the inevitable time when the new one fails.
Hi - I think the 88MY has an external fuel pump ...so tank-bang technique, while fun, may not be effective in this case?
Ahh yes you are correct - was thinking about mine at the time when writing my message.
Could still give it a tap though to see if anything happens.
You may need to have someone sit in the vehicle and turn the ignition on while you stick your head underneath to listen for the pump to come on. If not, then need to figure out why its not coming on. If so, then proceed as per Don B.
Hello!
I have recieved the crank sensor I’m the mail today. I have no clue how to install this bad boy / the location of where the sensor is. I couldn’t find anything on the web so I think I’ll go poked my nose around a little under the hood to see if it’s obvious
Front of the engine above the pulley/flywheel one bolt holds it in place. Take a flashlight to the front of the motor, scrape off all the muck and you'll see it.
I find the CPS easiest to reach by leaning over the right fender and reaching down around the upper radiator hose, so don't try to find it while the engine is hot.
Here's a photo I took while the radiator was out of our '93:
The sensor is held in place with just one 8mm screw, visible in the photo.
02-01-2018, 10:45 AM
