Fuel rail cooler, what's it off?
Discussion
Johno said:
Given its a P38 fuel rail, isn't it off a Range Rover wih Aircon ?
Apparently not. V8D have my car and have phoned the TVR parts people that normally supply them. They are all saying they have never supplied one. The guy who fixed my aircon a while back commented that it looked like the one fitted to Jag's, but it's not a Rover.Sorry Dave no P38 bits. I've never flown twin engines. One day maybe.
Right I found it.
BB, here's part numbers for the alternative parts list.
Jaguar series 3 XJ12 1979-85
CAC 3642 Fuel cooler.
CAC 3916 insulation sleeves (two required)
The part is no longer available from Jaguar, last list price was £105
It should be fitted with the straight pipe (outlet) on the side supplying the fuel pressure regulator and the A/C hose at that end connected to the evaporator.
The other end of the fuel cooler is an angled pipe connected to the fuel pipe.
The A/C at that end is connected to the compressor
BB, here's part numbers for the alternative parts list.
Jaguar series 3 XJ12 1979-85
CAC 3642 Fuel cooler.
CAC 3916 insulation sleeves (two required)
The part is no longer available from Jaguar, last list price was £105
It should be fitted with the straight pipe (outlet) on the side supplying the fuel pressure regulator and the A/C hose at that end connected to the evaporator.
The other end of the fuel cooler is an angled pipe connected to the fuel pipe.
The A/C at that end is connected to the compressor
shpub said:
eliot said:
If i was going to plumb any type of fuel cooler in my lines, I would do it after the pressure regulator on the return to the tank. This is LOW pressure and reduces the risks if you spring a leak.
TVR fitted it on the return side. I hadn't realised how it was connected by TVR. The fault with mine was spotted at TVR Power and Jason by-passed it.
I don't see that cooling the fuel being returned to the tank is very helpful. It may slow the build up of heat in the tank, but I didn't know that Griff's experienced a problem with this.
I assumed it was to counter high temperatures and vapourisation in the fuel rail.
As it's capable of taking high pressure fuel by design then if connected it were as Jaguar intended, I don't see a problem. Obviously, a low pressure fuel leak is better than a high pressure one, but it's probably going to burn in either case.
The original part failed because someone was ham fisted disconnecting it to get at other parts. This didn't make it leak, rather it kinked a pipe and was restricting fuel flow.
I don't know who that was, it might have been like it before I bought the car. Then gain, it was at TVR Power to put right what my local ham fisted independant had done, so if it was another example of his poor workmanship it wouldn't surprise me.
Refitting it as standard seems a bit pointless, even if I find one. If it's being refitted, then it might as well cool the fuel rail.
Will chilled fuel make much difference? Obviously it should help prevent vapour locks but will it make more power? I could see chilled fuel having more charge cooling effect, but I expect running the A/C would draw more power than I gain.
What about replacing it with a fuel cooler off another car? Any suggestions for a suitable donor that's more modern and the parts still available?
The idea was to help cool the fuel by reducing the temp of the stuff coming back from the fuel rail which can get hot and thus stop hot fuel from heating up the fuel in the tank. The unit also took the Aircon gasses after they had been through the heat exchanger. I have not connected it on the LS Cerbera - it got in the way.
To be honest it only does anything when the air con is running. When it is, the engine often runs a bit warmer so the fuel temp may be slightly higher than with the air con switched off. So there is a bit of a perpetual machine going on... air con cools the fuel but the fuel is hotter cos it the air con is switched on. Laws of diminishing returns comes to mind.
There are many Griffs out there without air con that don't suffer so I wouldn't worry about it.
To be honest it only does anything when the air con is running. When it is, the engine often runs a bit warmer so the fuel temp may be slightly higher than with the air con switched off. So there is a bit of a perpetual machine going on... air con cools the fuel but the fuel is hotter cos it the air con is switched on. Laws of diminishing returns comes to mind.
There are many Griffs out there without air con that don't suffer so I wouldn't worry about it.
eliot said:
Anyone got a picture of this fuel rail cooler?
Don't really understand why anyone needs one ..http://www.flex-a-lite.com/auto/html/compact-coole...
Thing I'd wait for symptoms like fuel vapouration before I looked for a fix..
Rev-erends photo is nothing like the original. The original is like a metal Liebig condenser with a couple of metal heat shields stuck on the sides. Except the A/C gas flows along the inner and the fuel flows through the outer jacket.
I can't take a photo until the car comes back from V8D.
The reason I was trying to replace it is that as TVR fitted one,I assumed they had found a problem and this was their fix.
I have only once had the hot fuel issue where it didn't want to restart on a garage forecourt. At that time the A/C wasn't working. I had the A/C put into working order soon after, but the fuel cooler had been by-passed by TVR Power previously, which I had forgotten.
The A/C has had to be disconnected to allow access to the engine. Before I have the A/C regassed I was trying to find a new cooler.
I had assumed that the fuel being cooled was the rail supply and not the tank return. As the fuel rail vapourisation problem happens with heat soak when the car stops, it's difficult to see how cooling the tank would help when there's no flow from the tank to cool the rail.
I was thinking that if I switched the A/C on prior to stopping I could pre chill the fuel rail so that when I tried to restart the fuel in the rail was less likely to have vapourised.
I can't take a photo until the car comes back from V8D.
The reason I was trying to replace it is that as TVR fitted one,I assumed they had found a problem and this was their fix.
I have only once had the hot fuel issue where it didn't want to restart on a garage forecourt. At that time the A/C wasn't working. I had the A/C put into working order soon after, but the fuel cooler had been by-passed by TVR Power previously, which I had forgotten.
The A/C has had to be disconnected to allow access to the engine. Before I have the A/C regassed I was trying to find a new cooler.
I had assumed that the fuel being cooled was the rail supply and not the tank return. As the fuel rail vapourisation problem happens with heat soak when the car stops, it's difficult to see how cooling the tank would help when there's no flow from the tank to cool the rail.
I was thinking that if I switched the A/C on prior to stopping I could pre chill the fuel rail so that when I tried to restart the fuel in the rail was less likely to have vapourised.
Well here the thing ..
think about it ..if you suffer fuel being vapourised after stopping - like in a petrol station on a hot day .. it's cause is a hot engine ..
The actions that take place are : you turn the ignition switch - this turn the fuel pump on and it stops as soon as the pressure is reached (2 ~ 5 seconds) there is approx 43 psi in the rail but it falls away gradually over time - you then turn the key to the starter motor position and crank the engine - now how much chance has the fuel had to be cooled ..
Now during cranking - I'm not really sure if the pump is reengaged - probably is..
Other EFI systems like Emerald don't have this fuel cuttoff system between cranking and keep the fuel circulating which in my mind would seem to flush out the hot fuel and the fuel being exothermic would remove the excess heat and be returned to the tank. A slightly better system in a way..
think about it ..if you suffer fuel being vapourised after stopping - like in a petrol station on a hot day .. it's cause is a hot engine ..
The actions that take place are : you turn the ignition switch - this turn the fuel pump on and it stops as soon as the pressure is reached (2 ~ 5 seconds) there is approx 43 psi in the rail but it falls away gradually over time - you then turn the key to the starter motor position and crank the engine - now how much chance has the fuel had to be cooled ..
Now during cranking - I'm not really sure if the pump is reengaged - probably is..
Other EFI systems like Emerald don't have this fuel cuttoff system between cranking and keep the fuel circulating which in my mind would seem to flush out the hot fuel and the fuel being exothermic would remove the excess heat and be returned to the tank. A slightly better system in a way..
rev-erend said:
Other EFI systems like Emerald don't have this fuel cuttoff system between cranking and keep the fuel circulating which in my mind would seem to flush out the hot fuel and the fuel being exothermic would remove the excess heat and be returned to the tank. A slightly better system in a way..
Actually they do cut off the pump. What should happen is the ECU fires the pump to pressurise the fuel rail. It then shuts down the pump until the engine is cranked over. During cranking the pump is activated but not in between. The reason is safety. It means that if a fuel leak occurs then switching the engine off or it stalling means that the pump is also switched off and doesn't force fuel through the leak. MBE do it this way... DTA do it this way... and I'm pretty sure that Emerald is no different. It is a safety issue.
As for this fuel vapourisation issue.... where has this sprung from? As most Griffs and cars do not have air con and don't suffer from this problem, I can't see what all the fuss about!
UF if you really want one... I have the one I took off the Cerbera. Email off line and make me an offer!
shpub said:
rev-erend said:
Other EFI systems like Emerald don't have this fuel cuttoff system between cranking and keep the fuel circulating which in my mind would seem to flush out the hot fuel and the fuel being exothermic would remove the excess heat and be returned to the tank. A slightly better system in a way..
Actually they do cut off the pump. What should happen is the ECU fires the pump to pressurise the fuel rail. It then shuts down the pump until the engine is cranked over. During cranking the pump is activated but not in between. The reason is safety. It means that if a fuel leak occurs then switching the engine off or it stalling means that the pump is also switched off and doesn't force fuel through the leak. MBE do it this way... DTA do it this way... and I'm pretty sure that Emerald is no different. It is a safety issue.
As for this fuel vapourisation issue.... where has this sprung from? As most Griffs and cars do not have air con and don't suffer from this problem, I can't see what all the fuss about!
UF if you really want one... I have the one I took off the Cerbera. Email off line and make me an offer!
Thanks for correcting me
Edited by rev-erend on Friday 1st February 14:22
Steve
The fuel rail arrived today. Thanks.
It's not the same as the Jag one that TVR fitted, but perhaps the later Griffs used the Cerb one.
It's shorter, and looks better made. The threads on the A/C conections look similar.
I won't have a chance to try fitting it for a week at least. Assuming the threads are the same, the only reason that the parts wouldn't be interchangeable that I can think of is if the A/C pipes are not long enough to reach the conectors on the shorter unit.
Once I know for sure, I will post up and complete the thread.
The fuel rail arrived today. Thanks.
It's not the same as the Jag one that TVR fitted, but perhaps the later Griffs used the Cerb one.
It's shorter, and looks better made. The threads on the A/C conections look similar.
I won't have a chance to try fitting it for a week at least. Assuming the threads are the same, the only reason that the parts wouldn't be interchangeable that I can think of is if the A/C pipes are not long enough to reach the conectors on the shorter unit.
Once I know for sure, I will post up and complete the thread.
Ballistic Banana said:
Lets me know AF if this is ok to ad to the alt list
BB
HOW VERY DARE YOU!BB
AF indeed.
I'll thank you to keep your mind off tool sizes when you address me sir.
The part fitted to my 1994 Griff 500 is 100% the part numbers I posted above.
The part number stamped into it matches the Jaguar part number. The picture in the parts list matches my part.
I have a print out of the parts list page if you want.
The only doubt can be if some previous owner had fitted this one in lieu of the original.
Steve thought the cerbie one was identical, so I assume he has seen the type he supplied to me fitted to an RV8 car. The only question is when they changed over.
I'll let you know when I have a chance to fit it, if the later type can be fitted.
Now I wonder if the A/C hoses are Jaguar?
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