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22.5 fuel pressure PSI cause poor running condition?


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Finally got a pressure gauge, hooked in after the fuel filter and at KF banjo (1973 2002tii) and I’m reading 22.5 PSI. Cleaned inline pickup screen and front banjo screen already. Car has been retrofitted with electrical pump at some point.  Do you  think this could cause my barely running, dies after revving symptoms, or time to dive deeper than potential fuel pump replacement? Thanks in advance!

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Yes you need 28-29 psi, you might try cleaning the pressure relief valve which is built in the fuel return nipple on the back of the pump, be careful when you disassemble the valve there's a spring inside that could shoot out to never-never land. When was the last time you changed the fuel filter on the radiator support? And checked the fuel pick up in the tank.

 

PS. Tii's have always had a electric fuel pump.

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If everybody in the room is thinking the same thing, then someone is not thinking.

 

George S Patton 

Planning the Normandy Break out 1944

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Yes, pressure is too low. I’ll bet flow rate is under specs too. All filters good? No nicks in delivery line?

Then new pump.

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2002 -73 M2, 2002 -71 forced induction. bnr32 -91

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Posted (edited)
17 minutes ago, Son of Marty said:

Yes you need 28-29 psi, you might try cleaning the pressure relief valve which is built in the fuel return nipple on the back of the pump, be careful when you disassemble the valve there's a spring inside that could shoot out to never-never land. When was the last time you changed the fuel filter on the radiator support? And checked the fuel pick up in the tank.

 

PS. Tii's have always had an electric fuel pump.

I’ll definitely try the pressure relief valve and thanks for the tip on the spring! Yes to the inlet screen, looked pretty clean and I did clean it up before putting back in. 
 

Fuel filter at radiator support has been 2 years now.

 

I misspoke in the sense it appears someone had switched to a 3 or 5 series looking pump when I looked at it last week. It’s on my list because to make a proper bracket because holy zip ties! Thanks!

 

IMG_9590.jpeg

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4 minutes ago, tzei said:

Yes, pressure is too low. I’ll bet flow rate is under specs too. All filters good? No nicks in delivery line?

Then new pump.

Every filter or screen except main at radiator support has been inspected and cleaned. Main is only about 2 years old, but have replacement to throw in. Every line I’ve inspected appears to be free of nicks or collapsed. Thanks!

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Another bizarre thing in chasing this down I ordered all the low hanging fruit maintenance items including rotor cap and button. The replacement cap is the same as I currently have, as it is marked, but rotor buttons are different. The button I received matches what should be on there, but is much different looking and doesn’t clear the cap when I install it. My old rotor button has no marking on it, any idea which one I need or what it is? I do have an optical eye on distributor and Crane xr3000 ignition. Thanks! 

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1 hour ago, e31fan said:

Do you  think this could cause my barely running, dies after revving symptoms

Sorry to differ, but No i dont think this marginal fuel pressure would give those symptoms....I  am sure that under full power condition this ~60% low pressure will cause misfiring and over-lean running...but at idle and dying after rev does not sound like a KF fuel supply issue. It could well be a KF adjustment issue, but i doubt its incoming fuel pressure if its still 20psi+.

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'59 Morris Minor, '67 Triumph TR4A, '68 Silver Shadow, '72 2002tii, '73 Jaguar E-Type,

'73 2002tii w/Alpina mods , '74 2002turbo, '85 Alfa Spider, '03 Lotus Elise

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18 minutes ago, Einspritz said:

What's your voltage at the pump while running?

 

The wiring to the pump as new is insufficient, so an old crusty, corroded wire may not provide enough power..., 10 ga. (US) Will be best.

I’ll check that, thanks!

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2 hours ago, e31fan said:

rotor buttons are different. The button I received matches what should be on there, but is much different looking and doesn’t clear the cap when I install it. My old rotor button has no marking on it, any idea which one I need or what it is? I do have an optical eye on distributor and Crane xr3000 ignition.

 

The one with a wide tip looks like the style used on the e21.  Typically, they are the same height.  Can you post a photo of the bottom side of them? 

 

I'm thinking someone may have shortened the wide tipped rotor to make it sit lower because the Crane disc on the center post cam is holding it up.  Photos of that would be nice too.

 

(For what it's worth), the e21 rotors have 1Kohm resistors built in and the stock 2002 rotors have 5Kohms.  Usually, they will say 1R or 5R on the underside of Bosch rotors.

 

I shorten the rotor for my distributor because I added a custom points holder.  It's easy to do on a belt sander.

 

IMG_2674.thumb.JPG.84fe7a17e8c0abef979185221354d720.JPG

 

IMG_2675.thumb.JPG.e7353e4ab1cb7c127d9766b5f86f6784.JPG

 

 

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I can give you peace of mind about the Crane(allison) photoelectic system. I replaced my points over 47 years ago with an Allison Photoelectric system and its worked fine for 440K + miles. Always have the ignition perfect before blaming the fuel. I'm no Tii guy, its Webers forever but I also think the slightly low pressure is the main problem. Your on the right track making sure the ignition is perfect.

 

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Well your trouble shooting has uncovered one problem low fuel pressure and this needs to be fixed before moving onto the next if any problem area, I'm not sure that 22.5 psi into the pump is going to get a high enough pressure to open the injector 420 psi per Keith. I will second the Alison comments by Greg mine is so old it was manufactured by A&E products the predecessor to Alison. 

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If everybody in the room is thinking the same thing, then someone is not thinking.

 

George S Patton 

Planning the Normandy Break out 1944

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I've never had a height problem with the rotor , using the correct trigger wheel? The Allison(Crane)system requires some more wiring than a Petronix  but is a better system in my mind, it's always started my Webers with ease.

 

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As Greg just said the wheel is very thin as it needs no magnets to trigger it just a thin shutter wheel

If everybody in the room is thinking the same thing, then someone is not thinking.

 

George S Patton 

Planning the Normandy Break out 1944

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