I have 32psi fuel pressure, and working injectors, car will stumble when cranking over and run with starting fluid. I'm going to test for continuity and resistance between the injectors and their ground and also between the injectors and ecm. Any other suggestions? Thanks.

 

The injectors are powered at all times by a relay and 1 wire, let me look for it , this power is " sitting " on them looking for a ground ( 12 wires ) provided by the ECU as in ground seeking

32 psi seems low as the inline 6 is 43 psi , looking in Jaguar 801S doc

 

Nominal pump delivery: 26.45 gallons per hour at 43.5 psi (3 bar)

Pump specs page 207 as copied

See also page 209 fuel line / pressure regulator of the 801s doc , link coming

801S TITLE

There is a specific fuel injector relay ( large right # 5 ) on the V - 12 and for the X305 is a repurposed relay accounting for the V - 12

You should be able to swap relay with a headlight , fog , or A / C clutch of the same part #

With you reading 32 psi see if it bleeds down over short time , there are check valves in each pump and one bad will compromise whole fuel lines pressure

One trick you can try is several cycles of the ignition switch to " charge " ( different then cylinder priming ) the fuel lines before starting attempt and fuel pressure reading

In the starting sequence only using the # 1 fuel pump...............

The # 2 will not come on until 4000 rpms

Check for burnt sockets at the # 1 fuel pump motor and swap # 1 fuel pump relay ( burnt power contacts inside), both of these are signs the # 1 fuel pump is giving out arcing across these components

Someone recently mentioned the relay can be opened by a trick and contacts cleaned , by this may pertain to smaller low power peanut relays like in security system

On another approach the cylinder walls may have been put into a Bore Washed condition , starter fluid only exasperates this condition of lowering the cylinder compression reading for successful light off or carrying on forward

The ECU has a specific external ground strap , at least on the inline 6 ECUs

 

Hi friend, thanks for replying. Based on drawings I saw the relay grounded the injectors, 44 psi is under load, 32 is idle. Did you check page 209? Blessings

 

Also I do have at least one injector working as it will stumble when cranking over on the same cylinder(s)

 

Double checking the relay grounding the injectors statement

The fuel pressure regulator should be independent of engine load but is manipulated only by manifold vacuum line hose pressure ( engine load ) ) old school way and will reach 46 - 47 psi fuel pressure at higher rpms , steady 43 at idle

This in effect gives a extra amount of fuel charge into cylinders along with ignition timing advanced

 

I take that 32 psi observation back you saw as I read the 801s doc more carefully

My pressures observation is at idle from my inline 6 as do not have V - 12

The FPR ( probably the same Jaguar part # ) should function the same way between both engines

 

Sorry yes you're right it's influenced by vacuum and not load. Here's a screenshot of page 209. It shows what I'm saying about fuel pressure. Also about the injector circuit you're right, I don't know how to read the diagrams too well. Also I attached a wiring diagram

 

Might be looking at a main fuel line filter change to cover base , bad tank fill as heard of a few , but this may pertain to quality of fuel and not dirt in fuel clogging filter

Flow arrow on filter points car's left

 

Also I do need to solidify my diagnostics Saturday. I'm sure I was getting 32psi cranking. But it wouldn't automatically go there when I turn the key, it would hover at 20, it would take key cycles and time to build it high, the pump would go to 60 unregulated though. But again, I need to do more testing before anything else, thanks again.

 

The force is not with my brain today

20 psi would seem to be a imposable pressure to start as the amount of fuel " charged " into cylinders is 1 / 2

The injector time open pulse width should be fixed and not adjusting

the 20 may be a sign the # 1 is giving out

There is a way to directly command the # 2 fuel pump to be used in the start and below 4000 with a jumper between socket 3 and 5 of the # 2 relay , this will drain battery with the keys in pocket ( hot at all times )

 

Remember I can build 60psi unregulated. I'll keep this thread updated.

 

60 as a no flow does not mean it can be balanced in a trade off as a volume flowing pump

60 going into the plumbed together regulator is a good thing as there is some flow back to tank as it regulates but this in comparison to the injectors flow (tank return flow will be much higher than injectors flows in starting )

But a good thing to observe and register

 

Either I my pump lost the ability to build good pressure or I falsely remembered I could build 60. I'm thinking my pump lost the ability to build 60. When I turned the key on the pressure would go from zero to 60, now I have to cycle it to get it from 0 to 38.

 

By cycling key to get to 38 you have either underperforming # 1 pump, either pumps check valves , FPR leaking ( check the vac hose for being wet as should not be ) an injector stuck open

Easiest thing is to jumper # 2 fuel pump relay

The is a secret fuse that must have the right or left heelboard fuse box relay close to close the fuel pump relays , swap with left engine bay fuse box

 

Pressure will hold so my valves are good, I'll try to active the other pump and see if I can get it. This is unregulated tests.

 

Update, I dead headed both pumps at the same time and they can only make 38 psi, I ordered two new pumps but with a slightly different part number, last 4 numbers are different. Two pumps dying simultaneously seems highly unlikely, but it's non zero odds.

 

agree on the 2 dead / underperforming pumps as the # 2 maybe gets 1 / 4th the duty time as # 1 but the calendar age the same

with both pumps powered at same time should get you above 38 , so looks like bypassing ( FPR vibrates ? )

There are some tubes in the fuel tank that others have run across , the diagram in the 801s doc not quite accurate

38 may be good enough for a start , maybe and may look at other V - 12 starting issues like maybe a Bore Wash condition

That secret small 5 amp control fuse controls both pumps and may not be clamping relay closed tightly unless an over center power contacts relay ( unknown but you would expect to be )

The 7 circle double hash is pump # 2

Note that both control powers go through the BT - 4 connector above the fuel tank

Do not remove as troublesome ( breaks lock pin then your shot ) but do check to see the tie wrap is on the lock bar holding halves together

That right heelboard fuse box relay must be clamped closed hard enough also so swap with left engine bay fuse box relay ( only controls car horns )

 

I had two bad pumps. Bought the car as a non runner, put in the cheapest pumps I could find (literally $19 each) and it’s been a dream ever since.

 

I replaced the pumps, unfortunately they're shorter though. Now I can deadhead a healthy amount. But my pressure regulator is dead too. When I pinch the return line off I can hit high enough pressure. So 2 pumps and a regulator died at once. But when I'm over 40psi of fuel pressure the car still stumbles when cranking. So, I have some injectors that aren't firing.