In vegas, and now having a hot start problem

Started By: James on 2014-05-02 07:18:02

I have a 87 jaguar sovereign, (it's pretty much a 91 van den plas with the 3.6l engine). Anyways, around two weeks ago it started to have "hot start" issues. Meaning if I drive it for around twenty or more minutes, and cut it off it takes around an hour of "cool down" time for her to restart. It has of started when we hit the "90's range". I spoke to the only jaguar dealer in Vegas and he said that it is due to "vapor lock". I have since changed my fuel filter, air filter, fuel pressure regulator and fuel pump....and guess what....happened again yesterday when we were high 80's. I was stuck at kmart parking lot for an hour before she finally restarted. She has never ever stalled, and does not feel sluggish when I use her. Does anyone know how to prevent "vapor lock" or what else it might be? I mean the jag dealer said it was "vapor lock" and if that's the case, what can I do to prevent this from happening again....please help


Hi Jamez,
Although I am not an expert I will help get the ball rolling for you and hopefully some people with names like Steve and George will jump in. Could be that fuel is vaporizing at the fuel pump inlet, or vapors from the charcoal canister are entering the intake. What about the intake air temperature sensor and the mass airflow sensor. The MAF measures the temperature differential and sends its info to the ECU which determines the amount of fuel injected, seems to me that if the MAF heated element senses a very hot condition it would tell the ECU not to inject fuel until a cooler condition is reached.
Hope this helps
David H

Jamez first things first---How can you have a 1987 VDP with a 3.6 engine? Do you mean a XJ40 ? or do you have a S3 XJ6?

Edited on 2014-05-02 17:52:31
It is actually a 1987 Jaguar Sovereign IMPORTED From England, as in right hand drive. The parts that cross referance the most is a 1989 Jaguar VDP. So I guess, yes a xj40 is another equilivent. Do you have any ideas or suggestions on what it is and how to fix it. It's only getting hotter here on vegas and the problem is more and more frequent as temp increases

Ok, but is it an XJ40 or an XJ6 SERIES III




Jamez it is tough to help you with the information so far. You said it is a 1987 but is "pretty much a 1991 VDP" and in the next post it is "more like a 1989 VDP. In those few years there were a lot of changes in several critical areas and engine management was at the top of the list............Further when you have a "hot" restart issue what are the symptoms? If in fact it is vapor lock I would start by making sure the fuel I used was premium and if that did not help I would attempt to help the fuel temp by wrapping the intake lines with insulation of some sort. Some folks swear by foil wrap and clothes pins. It is odd that this symptom just started this year--what have you changed from the previous season. You changed the fuel components but you did not say why. Did you do a fuel pressure test? Have you done a pressure test since the issue started? Throwing parts at a problem is frustrating and costly. I think I would check pressure and spark the next time the issue comes up. I think you may find the issue is electrical.

From all the info Jamez has given, I believe he does have a 3.6L XJ40. The XJ40 was sold in the UK a good 13 or 14 months before they were sold here in the States. There may have actually been some that were registered as 1986 models, I'm just not positive of that after all these years.

Those cars had the suspension mounted fuel pumps and some were plagued with tendencies to vapor-lock. Jaguar published a bulletin advising adding a second parallel fuel pump to combat that. I don't have all the old bulletins with me right now, so I can't come with it at the moment. It was a rather salty fix, but it did work; and strangely there were many cars that never had a hint of the problem, while others suffered routinely. Sounds to me like Jamez may be one of the cars that suffers.


Edited on 2014-05-03 0:59:42
Edited on 2014-05-03 0:53:41
It is a 1986 jaguar sovereign, but they did not make this model in America at the time. It looks just like you VDP, Meaning it has the "squared" headlights, with the self leveling suspension. To make it easier for you....and me, go to, and on the left enter my UK reg number "D764 FOR". It will literally tell you what car it is. and the reason for the "vapor lock" theory is for when I brought it to the jag dealer, he is the one who stated that the xj40's....early models had this issue and he did mention the "dual fuel pump" modification like Steven mentioned. the jag dealer said, try changing out your fuel pump and if that don't work....sorry there is nothing else we can do. He said he would not know where to start with the dual fuel pump for he does not have the diagrams, but of Steven can supply that, that would help me out a lot. The issue first started a few weeks ago, and the reason was when I was driving it in England it was never 90 degrees, it left England Feb this year and I got it cleared through customs and registered in nevada in April. So the problem is new for it never dealt with this heat before. If you want pics I can send them to prove that it is an import, likewise the reason for changing extra fuel components was to simply "asssist" the fuel pump with the vapor lock. Thank you all for your reply and please do not stop helping me sort this out. I would like Steven to please deliver the fuel pump information, and George pkease.....your expertise will help more then you think once we sort out which car it is. I can send a pic of the car and under the hood if this helps...please keep the ibformation coming. And I do use premium fuel, usually shell, but last fill up was at a maverick gas station. My issue George is that when I try to start it in the turns...turns...turns....until I stop. I can drive it to the gym and back in the morning.. no issues. Drop the kids to school in the issues, but pick up one of them in the afternoon....wont restart in parking lot of first child, if I cut it off. so I usually just leave it on until I get both and cut off at home. Also have massive pressure whenever I open up gas cap if that a lot and for a long time, I have never seen a car give me that much pressure....ever, not even in the desert heat of Qatar.

Please tell me you can find or have access to the parallel fuel pump informtaion.

I would agree with Steven you have fuel pump chatter which leads to engine stall on hot days. The fix is dual fuel pumps. The fuel pump is mounted on the chassis just in front of the left side muffler, and behind the left rear wheel, it is relatively easy to remove. However I would use a Jaguar dealer or a VERY KNOWLEDGABLE independent to carry out the fix.
Good luck

Edited on 2014-05-03 9:12:48
David, George and Steven,
Do any of you guys have the info for the parallel fuel pumps? For the jag dealer.does not. Likeiwse the brand new pump I are saying is defective? and if we can not come up with the dual fuel pump, will wrapping all my fuel lines in heat sleeves help? And side ac system has parts removed (awaiting delivery from england) would that in any way affect the vapor lock? has yet to stall...just won't crack after it has been running in the heat or parked in direct sunlight.

Edited on 2014-05-03 15:03:02
Jamez, you are getting a lot of attention.

Jamez, I have that stuff somewhere. First of the week I'll try to dig it up. Give an email address and 'll send it along.


Thank is

I am thinking of wrapping my fuel lines over the manifold as well as the fuel rail with "heat wrap", does anyone think this will help? The fuel line is not long at a, nothing but a few inches but instead of using "clothes pin" I want to use something more "professional" as a temp fix. Any inputs?

James you can certainly do that but the beauty of the clothes pins is --if that is not the fix they can be removed.

Quick question.... on my fuel line under the hood, before the fuel rail, there is a "disc shaped" part on the line. Now I don't know what it is, but I wrapped it in heat tape, would that in any way hurt my car? And what is it? And on a side note, any one know where I can get an a/c condenser at?

Not sure about wrapping, but it could be the fuel pressure damper.
Coventry West, SNG Barrett, Jag bits, Welsh Enterprises, check out their websites

And what does the fuel pressure damper do???

Hi, Jamez,

Twin pump bulletin is on the way.

The pressure damper reduces or eliminates the hydraulic pulses that result from the injectors opening and closing so rapidly. Without it, an audible 'knock' sound can be heard in the passenger compartment. Very annoying.

Good luck!

NO HOMO.... I love you brother. will he awaiting the paperwork

Got it and did price checks.. looks like most of these parts are going to have to be from a jaguar dealer. That's why I call her my "boat". Time to Bust Out Another Thousand.

Hello I'm in Arizona I'm having the same exact problem if Steven or James still have the info on putting in the duel fuel pumps please email it to me I would really appreciate it thank you