Measuring fuel pressure on a 4.5

[Imran999]

Has anyone measured fuel pressure on their 4.5?
Can’t work out what sort of test kit I need to get, I.e. what fittings etc.

The 4.5 fuel rail only has 1 inlet, 8 injector outlets and 1 similar style outlet for the fuel pressure regulator. No spare connections :-(

Was looking at a kit like this:


But as far as I can tell, the only viable option is a T-style fitting between where the main fuel line attaches to the front of the fuel rail (with a 90degree connector).

Any help would be hugely appreciated.

Thanks

Edited by Imran999 on Friday 25th June 06:12

[ukkid35]

I also wondered how to do that

In the end I decided it would be easier and cheaper to buy a new fuel pump and pressure regulator

Not done that either though

[Byker28i]

Remove fuel pipe, turn on the pump and measure distance it spurts? Or more sensibly the amount of fuel it delivers in a time period?

[TwinKam]

I had one of those kits and most of the connectors are of little use to man or beast.
Agree, the 'T' is the best option.

[Imran999]

Well thanks chaps for the input.
Byker28, I did actually run the fuel pump into a jerry can, and got very happy when I drained the tank in a matter of minutes. But then realized it was a meaningless measurement as it wasn’t under load.

Paul, I was tempted to just swap the pump, but all I can get here in Canada is the higher flow Bosch 044 pump. In a prior post you had indicated that the higher current draw from this pump could overload the wiring, so I was scared off that option.

In another post, you had tracked down a single faulty injector on your 4.5 (cyl 1), and I was wondering if you had good success with the BA version (higher impedance of 16ohms)? The D1720BA injectors are readily available here and pricing isn’t bad - I’m contemplating just putting a new set on (still running the originals, and had them cleaned once).

[CerbWill]

Imran, what issues are you having that's making you suspect fuel delivery issues?

[Imran999]

CerbWill said:

Imran, what issues are you having that's making you suspect fuel delivery issues?

Since arriving in Canada, the car has simply never run right.
I found thick sludge in the bottom of the fuel tank and so removed it to replace the in-tank filter and also had it cleaned out professionally.

After a new fuel filter and getting the injectors serviced/cleaned, I cleaned out the fuel rail, ran a lot of fuel through the system and then put it all back together again.

I also changed the plugs, leads and coil packs.

It ran ok after all of the above, but not great.
Then I replaced the near side lambda and it suddenly felt a lot better, but it didn’t last.

Generally, it performs at around 7/10th’s and I’ve covered about 1000 miles since all of the above.

At the start of the summer I replaced both lambdas for some genuine NGK ones, thinking this would maybe improve things, but it didn’t make much difference.

This past week it has felt pretty awful again, and feels like either fuel starvation or misfiring.

I’m now thinking that I really need to do a full investigation into what is causing my problems and I’ve done a lot of reading on engine oscilloscopes.

I wanted to check the fuel pressure and then scope high and low tension ignition as well as injectors.

Edited by Imran999 on Saturday 26th June 05:01

[Imran999]

Oh, just realized that the supply from the pump (runs through the V) is connected to the fuel cooler with a hose clamp. The exit from the cooler (hose clamp) then runs up to a nice finished L piece that attaches to the front of the fuel rail.
Presumably, I can replace the fuel cooler with a T-shaped manifold that has a shrader type valve, and then I can check fuel pressure whenever I want?

A bit like this:



Of course, I can put it all back to normal, once I’ve got the beast running as it should - I remain hopeful

[TwinKam]

I believe that the cooler is post fuel rail, ie it cools the fuel that's being returned to the tank. So measuring the pressure here is pointless.

[Byker28i]

Forgive me for stating the obvious, but are your coils alright? Everytime I've had issues with the car not feeling right, hesitant, it's been the coils at fault. Fist time was it wouldn't run above 4k revs, just got lumpy, another time one coil was breaking down under load so one half of the engine wasn't delivering correctly.

Could it be it's something else and you've actually resolved the fuel issues?

[quote=Imran999]Well thanks chaps for the input.
Byker28, I did actually run the fuel pump into a jerry can, and got very happy when I drained the tank in a matter of minutes. But then realized it was a meaningless measurement as it wasn’t under load. [/quote}

Finger over the end or squeeze the hose and it should squirt even further (Joke - no don't do this)

Edited by Byker28i on Saturday 26th June 08:41

[Imran999]

TwinKam said:

I believe that the cooler is post fuel rail, ie it cools the fuel that's being returned to the tank. So measuring the pressure here is pointless.

On my car, the cooler is definitely pre-cooling the fuel. The pressure regulator at the end of the fuel rail, has a hose that connects directly to the return line on the bulkhead.

I did read previous threads where this was discussed extensively, it appears TVR did it both ways.

[Imran999]

Byker28i said:

Forgive me for stating the obvious, but are your coils alright? Everytime I've had issues with the car not feeling right, hesitant, it's been the coils at fault. Fist time was it wouldn't run above 4k revs, just got lumpy, another time one coil was breaking down under load so one half of the engine wasn't delivering correctly.

Could it be it's something else and you've actually resolved the fuel issues?

Imran999 said:

Well thanks chaps for the input.
Byker28, I did actually run the fuel pump into a jerry can, and got very happy when I drained the tank in a matter of minutes. But then realized it was a meaningless measurement as it wasn’t under load. [/quote}

Finger over the end or squeeze the hose and it should squirt even further (Joke - no don't do this)

Edited by Byker28i on Saturday 26th June 08:41

I also suspect ignition, but just want to rule out fuel pressure as a matter of course.

And don’t worry, I won’t be trying out your open-loop fuel pressure measurement methodology. Canadian homes utilize timber frame construction, so fire-safety consciousness is through the roof here.

[gruffalo]

Do you have the ability to plug a PC into the ECU?

The original software had quite a useful facility to view the ignition.

Basically a failing coil pack would have a messy looking trace in the software, not always but often so that could help diagnose your issue.

[Imran999]

Thanks Martin.
I do use a PC for diagnostics and setup, yes.
Noticed a tile bit of noise on the ignition trace but didn’t think anything of it.
Of course, what you’re saying makes perfect sense, if there is any fault with the coil, the signal reflections could get back to the ECU and show up as noise.
I was thinking there must be some easy way to diagnose a bad coil, this would be it.

Interestingly, everything looks good until the engine gets stinking hot, there must be some temperature related failure of the coil.

Thanks for the excellent input!

[mrniceguy351]

I relocated the coils to the inside of the fenders and all my missfire problems went away.

[Rufus Roughcut]

Imran999 said:

On my car, the cooler is definitely pre-cooling the fuel. The pressure regulator at the end of the fuel rail, has a hose that connects directly to the return line on the bulkhead.

I did read previous threads where this was discussed extensively, it appears TVR did it both ways.

My 98 4.5 is the same as yours, as per this diagram stolen from the internet.



Obviously we don't have an adjustable fuel regulator as standard and we have the fuel cooler between the pump and rail.

I would go with what you have suggested previously, pop one of the pipes leading to or from the fuel cooler and insert the gauge there.

[Imran999]

mrniceguy351 said:

I relocated the coils to the inside of the fenders and all my missfire problems went away.

“Fenders” was a dead giveaway that you’re not in the UK.
;-)
Whilst it’s not as hot here as Oz, it’s often 25-30degC in the summer.
Perhaps higher ambient temperatures necessitate relocation of the coil packs, or very frequent replacement?
Would really be interested to see/learn about your implementation - thank you so much for the input.

Edited by Imran999 on Monday 28th June 18:45

[mrniceguy351]

Imran999 said:

“Fenders” was a dead giveaway that you’re not in the UK.
;-)
Whilst it’s not as hot here as Oz, it’s often 25-30degC in the summer.
Perhaps higher ambient temperatures necessitate relocation of the coil packs, or very frequent replacement?
Would really be interested to see/learn about your implementation - thank you so much for the input.

Edited by Imran999 on Monday 28th June 18:45

The missfire issues I had didn't occur in the middle of summer, maybe 25deg?

I just cut the wires and soldered in extensions. The coils I mounted with a couple of nutserts. I also glued a strip of foam to the base of the coil, as the inside of the fender is slightly curved. Just make sure the coils don't get in the way of the air intakes.

[Imran999]

mrniceguy351 said:

Imran999 said:

“Fenders” was a dead giveaway that you’re not in the UK.
;-)
Whilst it’s not as hot here as Oz, it’s often 25-30degC in the summer.
Perhaps higher ambient temperatures necessitate relocation of the coil packs, or very frequent replacement?
Would really be interested to see/learn about your implementation - thank you so much for the input.

Edited by Imran999 on Monday 28th June 18:45

The missfire issues I had didn't occur in the middle of summer, maybe 25deg?

I just cut the wires and soldered in extensions. The coils I mounted with a couple of nutserts. I also glued a strip of foam to the base of the coil, as the inside of the fender is slightly curved. Just make sure the coils don't get in the way of the air intakes.

Thanks for the input here.
I wonder if higher ambient temperatures just shorten the life of the coils - a failure could well have occurred then, at some more modest temperature.
Did the standard HT leads fit, or did you have to find longer ones?
Thanks!

Edited by Imran999 on Monday 28th June 21:44

[mrniceguy351]

Imran999 said:

Thanks for the input here.
I wonder if higher ambient temperatures just shorten the life of the coils - a failure could well have occurred then, at some more modest temperature.
Did the standard HT leads fit, or did you have to find longer ones?
Thanks!

Edited by Imran999 on Monday 28th June 21:44

I used the MSD leads that were already there, after shortening them and fitting new "metal clip things" at the plug end. They ended up significantly shorter.