I've always had starting issues on my '92 V12. Symptoms are car will not start, or starts after a very long period of cranking (up to 10 seconds) on the first key turn. If it doesn't start on the first try, it will always start perfectly on the second try. If I prime the fuel rail by turning the ignition on and off a few times it will start immediately on the first try. There is no black smoke, it's not flooding, and once it's started it is as smooth as silk. If I turn the car off and then immediately crank it again, it will start first time, but if it's left for anything over 10 minutes, it's back to priming the fuel rail again, or a very long crank.

After fitting a fuel pressure gauge, it's clear to see that I have at least a problem with losing fuel pressure. I lose all pressure on the rail within 5 minutes. I want to fix this to see if that is the only issue I have, or if something else is amiss. My car has the extra fuel temperature sensor on the fuel rail, which triggers the regulator to boost fuel pressure for the initial 45seconds if the fuel temp is above 70deg, and from the fuel pressure gauge I can see that this system is working. (When the car is hot if I switch off, then restart immediately , the fuel pressure gets to nearly 50 psi for the first 10~20 seconds, then falls back to 40psi) When the fuel temp sensor isn't triggered, I need 40psi on the fuel pressure gauge to ensure a perfect start. As said earlier, I can get this by priming the fuel rail a few times.

Question 1 : I have been doing some reading and I know the check valve is in the fuel pump, which is in the tank. I'm leaning towards this being my issue and I have seen various posts on other car forums (non-jaguar) about people having similar issues and many have fitted a check valve to the fuel feed line from the tank to the fuel rail. They typically fit this check valve as close to the tank as they can. Has any one done this ? Are there any pitfalls that I'm not thinking about ?

Question 2 : I guess I could also be losing fuel pressure due to a dripping injector (or 12) but my thinking is that this would give me a nasty fuel smell and/or smoke from the exhaust when it eventually fired ?

 

I don't see any problem with an add-on check valve, personally.

I have to wonder, though, if your fuel pump is getting weak. Even if all the pressure has bled off it should re-pressurize almost instantly....on the first "prime" cycle. That's the way my (older) XJS and XJ6 were, at least....from zero to full pressure in 2-3 seconds

Cheers
DD

 

Hi Doug

Thanks for that. You may have a good point about the fuel pump. I know the car has had the tank out and "messed about with" by a PO so to be honest I'm kind of scared as to what I might find in there. As funds are a bit tight at the moment (just had my XJR serviced) I may try the check valve approach first, and will start saving up for an OEM fuel pump and do the tank job properly in the summer

Take care

Scott

 

So, I got a "real" fuel pressure gauge and have it installed in the car....

Sender connected into the top fuel hose that runs between the fuel rails....

(yes, it's proper fuel injection hose, and yes they are fuel injection hose clamps that are new and not reused)



Gauge mounted in the instrument cluster...





No Fast and Furious gags please. The gauge is only stuck on with Velcro so I can return to a normal dashboard for concourse competition work :-)

Here are more findings on the fuel pressure/hard starting issue.

I replaced the inline fuel filter as I didn't know when it had last been done. Unfortunately (for science sake) I did the fuel filter at the same time as I did the gauge, so I can't compare old fuel filter and new fuel filter to see if it has had any effect.

1. The gauge reads about 7psi before ignition on

2. At ignition on, the pressure climbs rapidly and tops out at just over 40psi

3. The instant the fuel pump stops running the pressure dies away back to 7 again.

Conclusion 1. My fuel pump is ok (as it can lift pressure up to 40psi in 1 priming 2 second cycle)

Conclusion 2. My check valve isn't (as I lose pressure as soon as the pump stops)

I then fitted an inline check valve in the engine compartment, just before the fuel hose connects to the inlet side of the fuel rail. With this connected, I got the following behaviour

4. The gauge reads about 7psi before ignition on (the first time after the fuel line had been opened and depressurised)

5. At ignition on, the pressure climbs rapidly and tops out at just over 40psi

6. The instant the fuel pump stops..... the pressure remains where it is at 40psi (for at least 10 minutes that I checked it over)

For a variety of reasons not to be discussed, I had to take the check valve out again, so I was back to the original behaviour, ie 1 to 3 above.

Now here's the funny thing...... the car now seems to start first time on the first crank, after only 1 priming cycle (the normal 2 second one which lifts the pressure up to 40psi) wheras before I had to prime the car 2 or 3 times to ensure a start on the first crank.

Could it be that my fuel filter was restricting the pump flow at priming and preventing the pressure on the rail recovering to 40psi ??? Thoughts on this would be welcomed

The original fuel filter was in a bad state..... lots of brown gunk poured out of it when I emptied it.

To be fair I've only ran it a few times this evening in the garage because it's raining outside, and it's a well known fact the XJSes can't go out in the rain, so I'll need to wait for better weather to do more testing and post back.

 

It's a shame that you didn't test the fuel flow through the filter from both sides before you changed it. That way you would have seen directly whether the filter was restricting flow or not.

ie outlet side disconnected run 2 second prime cycle, collect fuel in a bottle.
inlet side disconnected run 2 second prime cycle, collect fuel in a bottle and compare quantities.

Although it would seem that your filter may have caused restricted delivery and your pump is still working; albeit on overtime due to your tired check valve.

Can you not 'borrow' one on a more permanent basis?

 

Hi Translator

Thanks for the feedback.

You were referring to me borrowing something more permanently ?? What was that ?

 

Hullo Scott,

In your post '176' you mention that 'for various reasons not to be discussed you had to remove the secondary valve'.

Although when you fitted this it did seem to make a difference to your problem.

The "Borrow more permanently" I hope was taken in the right way. It is the sort of thing that I might do when trying to sort out a tricky problem.

IE my car no 1 has problem X, my car no 2, does not, and may well have the part required to fix my car no 1.

So to find out if this is the case before I spend money I may well swap the part from 2 into 1 to see if this cures or helps with the problem;

I will then need to either 1 refit the part back into car no 2, or fit the new part directly into car no 2.

I don't have access to any sort of local Jaguar Spares suppliers and so sometimes need to come up with all sorts of Heath Robinson type solutions before I bang in the old card details.

So I have "Borrowed" and then "replaced", but could not initially "Permanently Borrow".

Hope this makes sense, my brain is somewhat addled with trying to sort out someone's bad machine type translation.

You don't need to go into detail as to why you removed what appeared to have given you a good solution, but I am naturally curious.

All the best,
Richard

 

Hi Richard

I'm with you now :-)

I actually took it out for a few reasons. First one was that I had "cobbled together" the connections and I didn't feel comfortable with them and was scared of a fuel leak. I used to help out in a garage in the UK at the weekends and while doing a simple tune up for a customer (car was sitting running at idle, connected to gas analyser machine) the car burst a fuel injector hose. The images of the resulting fuel shower and fire as a result of spraying on a hot manifold will stay with me forever so I'm generally over cautious around fuel systems now.

Second one was that the check valve I bought was just a cheap one to try out the theory. Now that I know I have problems with the check valves in the pump in the tank I'm committed to doing the job properly in the summer by removing the tank and replacing the pump.

I've learned by watching my fuel pressure gauge when is the perfect time to crank the car, so it's kind of fun starting it up these days!

Take care

Scott

 

No such thing as over cautious with petrol, a similar incident happened at a garage I worked in, in 1980. The resulting fire burnt down the garage and destroyed 5 customer cars all imobilised and undergoing repairs.

A mechanic was doing some welding of a floor pan and cooked a fuel line. It looked like a WW11 raid on a fuel dump.

At least your pump is pumping and like you say having the pre-flight checklist can be fun for your passengers. What.

 

yikes~!~! the only fire I have been fortunate to escape was when I was at work too, we were framing an apartment and a guy knocked over a 100 pound propane tank and broke the valve off the top and the torch on the tank was lit, the top of the tank caught fire, ever see a 100 pound tank of propane under pressure on FIRE?
Scared the livin' crap out me and everybody else, we scrambled out of the building and went around to the front and watched the four storey wood frame building burn like toothpicks, guess what.....there was 18 other 100 pound propane tanks in the building as well as 45 gallon barrels of deisel next to the building and about every minute or two one of the propane tanks exploded sending a huge rolling ball of thunderous flames three storeys high with a cloud of black smoke. The deisel barrels caught fire as well so did a number of machines like loaders, plus the building next to it and a bunch of cars burned down. It was the most frightening experience of my life, I quit my job the next day.....ha ha ...no BS. So I DONT want to see a gasoline fire in my engine, and I intend on buying a fire extinguisher for my car since I am used to having one handy when I fly as a student pilot. I had a leaking fuel hose and had it replaced a couple of months ago. Where I live is over one million people and every fireman, firetruck and half the city cops and paramedics were there, everyone got out alive.

 

So, based on my encouraging results when I installed a check valve in the engine compartment (but then had to remove it again for various reasons stated before) I bought a better check valve and tried again....



Sorry, not a great picture, but the silver thing in the middle of the picture is the check valve installed in the flexible fuel line running over the left hand camcover towards the fuel rail.

With this installed (and no leaks) the car now performs as follows :

With ignition at position 1 (accessory) the fast and furious fuel pressure gauge does its "opening ceremony" (can never get tired of that!) and then shows a fuel pressure of 40psi (even after being left overnight)

With ignition turned to 2, fuel pump runs and pressure lifts to almost 50psi (and holds at 50psi even when fuel pump stops running)

Once I turn the key to crank, it's like telepathy.... the things bursts into life (not flames) almost before I've turned the key ! Realistically it's starting within the first revolution of the engine, which is a huge improvement compared to previous results, even with a 2 or 3 times "priming" with the ignition being turned off and on.

Then, interestingly, the idle drops off a little, from 750 or so to around 600 or 500. It does this for about 5 seconds, then the idle comes back up and then everything is normal again. This behaviour is consistent and repeatable when the car is warm, but not when it's cold. Based on the fact I installed the check valve way up in the engine compartment, and realistically as I know I have a faulty original check valve in the fuel pump in the tank, I imagine the fuel pressure behind the check valve back into the tank isn't as great as the pressure from the check valve forwards and into the fuel rail. This would seem to me to explain the minor drop off in rpms for just a few seconds just after the car has started. It doesn't do it when cold, probably because the fuel injection ECU is overfuelling the injectors on a cold start up so there's enough gas to make up for it.

Anyway, just thought I'd update the board in case someone else has similar issues. I will eventually do the fuel pump properly, but at the moment, this workaround allows me to keep enjoying the car fully. (There's nothing worse than coming out to an XJS convertable, getting a compliment from a passer by on how nice the car looks, then the bl**dy thing cranks for 30 seconds and doesn't start !)

 

Great that you got it working. I have a question about your theory about the short drop in idle speed.

When it drops, do you see a drop on your mission control fuel pressure gauge, because if you don't then to me it doesn't seem logical that this is related.

Your fuel pump and new check valve are obviously working fine.

Cheers

 

Hi Richard

I was meaning to update my post, but I have been too busy enjoying the car !

After the first day when I posted, and had seen the drop in idle 4 times after hot restarts, it has never done it again.

And to answer your question, the fuel guage didn't dip during the lower idling, so you have a valid point.... with all this diagnostics I have now, I can effectively rule out fuel pressure issues. It must have been "something else" !

Anyway, it's gone away now, and the starting is still telepathic, so all's well that ends well

Take care

Scott

 

I know this is an old thread, but I am having a similar problem with a different make car.

Do you remember where or how you acquired the check valve you show with the OUT embossed on the cover? Also, is the valve truly rated for fuel injection (high pressure) service?

Thanks for any reply.

 

@mahunt

I got it from a website that specialized in parts for airplanes...... I reckoned their standards would be higher than for cars

Summit racing sells good proper spec check valves for around $50, and they are usually really good at answering your questions on the phone if you want to call them to check

 

Guys

Thanks for all the information in this thread - based on your experience I would appreciate your opinion

My very standard V12 etype with 4 Strombergs has a issue which we feel is fuel as we have had all the Valves and Ignition checked, the symptons are:

Starts fine when cold
1Revs flatten out with a muted tone when accelerating hard in 3rd and 4th - if I back off and accelerate very gently I can get it up higheroff and accelerate

 

b The fuel pump seems to opertate well and can fill a litre bottle at the fuel rail in ~ 10 seconds.

I am thinking that this is a fuel pressure issue on the fuel rail - what do you think - does this sound like a dodgy fuel return valve?

Thanks in anticipation

 

Guys

Thanks for all the information in this thread - based on your experience I would appreciate your opinion

My very standard V12 etype with 4 Strombergs has a issue which we feel is fuel as we have had all the Valves and Ignition checked, the symptons are:

Starts fine when cold
1Revs flatten out with a muted tone when accelerating hard in 3rd and 4th - if I back off and accelerate very gently I can get it up higher
2 When hot and having stood for several minutes The engine struggles to start within 30 seconds of turning over
a I have tried removing the fuel filter = no difference
b The double fuel pump seems to operate well and can fill a litre bottle at the fuel rail in ~ 10 seconds. I have replaced the inlet pipe as the old one may have been kinked

I am thinking that this is a fuel pressure issue on the fuel rail - what do you think - does this sound like a dodgy fuel return valve?

Thanks in anticipation

 

You might do better to post this on the E Type forum. The previous thread dealt with fuel injection engines, and yours has carburettors. The fuel feed you tested of a litre per 10 seconds is plenty of fuel feed, even for a V12!
So it is far more likely your problem is either ignition related or a carburettor malfunction/fuel blockage in the actual units.


I would start by removing the carbs and taking them apart and looking for crud and blocked jets. It is, however, just as likely that an ignition problem, only showing up under load and higher revs, is robbing you of power. First thing to test would be the coils.
Greg

 

Is 8mm the right size for a check valve for the hose before the fuel rail?
thanks. here's one i'm looking at: