Pressure regulator replacement

swindonwedge · Post by **swindonwedge** » Tue Jul 05, 2011 11:10 am

OK - first I'm new to this so go easy please!

I have a TVR 350SE with a Rover 3.9 V8 which was running fine for about 700 miles after I bought it but then developed a very noisy Fuel pressure regulator. I bought a straight replacement part and fitted it, so far so good.

However, now there's no fuel in the system, I have gone as far back as the pump and when turning it over not even any fuel coming out there. So my question are - is it possible having air in the system has caused teh pump to fail? Will I be able to manually prime the system and will this work or should it be self-priming?

For further information the idle speed of the engine has been a bit all over the place, sometimes up to 1750rpm, other times as it should be about 750rpm. Is this likely to the regulator or pump or both or even something else?

I'm sure I'll get used to fiddling with the car over the coming months/years but for now its a steep learning curve!

kiwicar · Post by **kiwicar** » Tue Jul 05, 2011 12:13 pm

Hi
Is this on EFI? because if it is the fuel pump is driven off a relay which in turn is controlled by the ECU, the relays do fail (well in my Range rover it did!) so worth a check that you have volts at the pump (or just replace the relay they aren't expensive). If it is an in tank pump then check the earth strap, check the pump is still attached to the bit that goes into the tank with the float on it and have a good check over the wiring going to the tank with a volt meter, make sure the ECU is giving it's priming pulse.

If it is on carbs the fuel pumps (I presume it is a facet) are prone to just stop working. When they do work they are primed by being installed below the tank (actually I think they will self prime to a height of about 8 inches, but generally best installed below the tank).
Best regards
Mike

swindonwedge · Post by **swindonwedge** » Tue Jul 05, 2011 12:54 pm

Its an EFi though the fuel pump is below the fuel tank(s) so can easily check for power to the pump which I'll do later when I get home. If there's power getting to it but no noise/petrol being pumped I guess it'll be a new pump!

DaveEFI · Post by **DaveEFI** » Tue Jul 05, 2011 1:31 pm

swindonwedge wrote:Its an EFi though the fuel pump is below the fuel tank(s) so can easily check for power to the pump which I'll do later when I get home. If there's power getting to it but no noise/petrol being pumped I guess it'll be a new pump!

If it's a flapper system, the pump only runs with the starter motor turning and then when the flapper moves with the airflow of a running engine. To run the pump with the engine stationary, remove the intake ducting to the flapper and move the flap with a finger.

SuperV8 · Post by **SuperV8** » Tue Jul 05, 2011 3:08 pm

If it's a flapper system, the pump only runs with the starter motor turning and then when the flapper moves with the airflow of a running engine. To run the pump with the engine stationary, remove the intake ducting to the flapper and move the flap with a finger.

I spent many an hour trying to fault find the pump only to find it worked fine when I moved the air flow meter flap with my finger!

I believe the 350se's were all hotwire (well if you believe wikipidia!!!) Is yours hotwire?
As mentioned above i would check the fuel pump relay, not sure how hotwire controls the fuel pump, so you may have to check for volts at the fuel pump when cranking as the pump should definatley be running then.

Tom.

swindonwedge · Post by **swindonwedge** » Thu Jul 07, 2011 3:05 pm

Yes it is a hotwire, and not sure how it all works either, though I'm findong out pretty quickly! Hopefully be under her again this weekend so will be able to update with where volts are getting to!

DaveEFI · Post by **DaveEFI** » Thu Jul 07, 2011 3:28 pm

swindonwedge wrote:Yes it is a hotwire, and not sure how it all works either, though I'm findong out pretty quickly! Hopefully be under her again this weekend so will be able to update with where volts are getting to!

All the injection systems I've come across stop the pump with the engine which makes fault finding more tricky. This is to prevent fuel spillage in event of an accident, etc.

I'd guess the hotwire controls the pump from the ECU. It will need to see a tach signal from the ignition coil to run it. But will usually run it for a few seconds when you switch on to prime things.

However, it will be switched by a relay, so you could remove that and feed 12 volts to the pump direct, to test the pump itself. You should be able to hear it running in a quiet environment.

swindonwedge · Post by **swindonwedge** » Wed Sep 14, 2011 2:24 pm

Turned out it was an electrical issue, the automatic cutoff had damaged connections (not helped by me I suspect when replacing the regulator

)

So the question now is as its an adjustable regulator how do I get the fuel pressure right to the rail? I know it needs to be 39-40psi but without a fuel pressure gauge hard to test! I'm thinking my options are take it to a garage to find out, run it and listen to it then check the exhaust for the colour of the deposits.

Any ther suggestions? I've tried to have it open as much as the old one was as they are the same part but am pretty sure this isn't fool proof and I don't want to run it too rich or lean for too long!

swindonwedge · Post by **swindonwedge** » Tue Oct 04, 2011 1:08 pm

Now up an running and working...well sort of, if it was fine I wouldn't be posting here now would I

Anyway up to 3000-3500rm it seems fine and sounds as it should, then completely runs out of puff and takes forever to get to 4000rpm so no acceleration. Is this just likely to be it running lean or do I need to look for something more fundamental, it seems an odd behaviour to me.

DaveEFI · Post by **DaveEFI** » Tue Oct 04, 2011 2:11 pm

If it's adjustable, likely not a factory fit. And they do sometimes make a groaning noise when set to the lower end, pressure wise, as these engines need. It's probably also a rising rate unit. Just how well these work with a hotwire, I dunno. They can improve the running of a flapper system - but at the expense of fuel consumption.

I'd suggest you get a gauge and set it to the correct value. There's usually a port on the unit the gauge screws into. Or just try adjusting for the best idle.

ramon alban · Post by **ramon alban** » Tue Oct 04, 2011 5:57 pm

swindonwedge wrote: I know it needs to be 39-40psi but without a fuel pressure gauge hard to test!

I've tried to have it open as much as the old one was as they are the same part but am pretty sure this isn't fool proof and I don't want to run it too rich or lean for too long!

Hello Dude(?), The lack of power might be attributed to either rich or weak mixture, and if you are persuing an incorrect fuel pressure, then buy a cheap foot pump,

http://www.amazon.co.uk/Polco-Single-Barrel-Foot-Gauge/dp/B0001P0IVA/ref=sr_1_2?ie=UTF8&qid=1317749253&sr=8-2

unscrew the gauge, fix it to a length of high pressure fuel tube and introduce it to the fuel rail, probably with a tee piece and three suitable fuel hose clips.

If you cant manage that, you can learn a lot about the status quo mixture from spark plug colour, one from each bank.

Sooty black, too rich, reduce the fuel pressure and try again.

Bright white, too lean, increase the fuel pressure, you get the idea?

Before getting too deep into component failure and the random, costly replacement thereof, please be aware that the majority of Efi faults in our period systems are due to connection problems and rogue air leaks into the plenum chamber, so that should be No 1 priority to chase those potential issues away.