First thanks for the advise on fuel pressure testing all sorted now, I have tested with 2 gauges and I am getting 4.5 to 5 bar on ignition on, seems high?

Howeverthis is now the problem I find. (car is an XJR-6)
Car will not start.
1. Ignition On = Fuel Pump 1 runs for 2 secs as it should to prime the system.

2. When cranking the engine will not start (sometimes tries a little stutter but no go)

3. I check and find Fuel Pump 2 not running,

4. When I bypass the 2nd Fuel pump relay with a jump lead then Pump 2 runs (all the time ignition on or off) and car will start and runs fine.

5. Checked all fuses and relays and can find no cause.

**As a matter of course as I had them in stock I fitted a new Pressure Regulator and Fuel Filter in a vain desperate hope that this may somehow cure the problem, logic says this would make no difference I know but after spending so much time I was clutching at straws!
Any advice very welcome

 

Relay not doing its job?

Car should run on just 1 pump no problem.

 

Not sure what your reply means? If I by-pass pump 2 car runs fine so not a spark problem.

 

Thanks for reply
Car will not run on cranking over unless I by-pass manualy pump 2 relay. If I bypass pump 1 relay this will still not let the engine run. If I turn on ignition I can hear pump run but car will not start howver if I jump relay for pump 2 it will run. Could it be that pump 1 although priming the sytem to pressure will nnot run after the initial 2 seconds?

 

It's not uncommon for the pump outlet pipe to drop off the pump in the tank. So although the pump runs it is not delivering fuel.

That doesn't explain your fuel pressure readings though. Could that be residual pressure from running on pump 2?

 

Hi
Good thought, I have been over it so many times perhaps I need to stop and start again. I will try again taking note of your comments and let you know
Thanks
Dave

 

The # 2 fuel pump does not come on until 4000 rpm then off as it drops under 3200

The # 1 fuel pump will only run for 3 - 4 seconds and then back off

The # 1 fuel pump will then turn on for the duration of the drive from the Crankshaft position sensor seeing engine rotation

If the # 1 will not start the engine the # 2 will come on after a point I don't understand but someone else does

This can confuse troubleshooting if the starting sequence has other problems other then the fuel pump ( s )

The initail 3 - 4 second priming of the fuel lines can be resolved by cycling the ignition switch 5 times to the on position without start position , hold the key in the on position for 5 seconds on each cycle

This will only overcome a slight loss in the " trapped " line pressure

This trapped pressure ( 43 PSI = 2.96 bar ) is time dependent on the last time it was pressurized

There is a condition called bore wash you may have put the cylinders into where once you try to start the engine there is not enough compression to " maintain fire "

A over high fuel pressure will wash the cylinder walls of piston ring sealing lubricant setting you up for a no start

This will throw off your troubleshooting

As the fuel pump is failing on the brushes , it will arc and damage both the fuel pump relay internal power contacts ( even though it clicks getting the correct control command ) as well as burning the connector sockets at the fuel pump motor

You can swap the fuel pump relay with the ACC relay on the same row on the inboard side

The BT4 connector above the fuel tank can come loose and intermittent as it comes loose . this carries the control circuit from the # 10 fuse right heelboard fuse box . wire # 30 Pink / Brown wire

Be very carefull in putting this connector back on to not break the locking pin

This # 10 fuse also powers the OBD 2 port that someone found the power pin of the connector port bent over and shorting out

During the heat of battle the ECU voltage can't get below 11.4 volts or the fuel injectors will not cycle open although the engine starter will rotate fine

Any questions - just ask

 

You can have a intermittent ECU controlled relay ( large # 5 ) in the engine bay that powers the fuel injectors . You can swap this with the same part # relay like the headlight , fog light or A / C clutch relay

This ECU controlled relay is controlled by the ECU and brings power back into the ECU along with power " sitting on " your fuel injectors . This is your 2nd power for the ECU

The 1st power to the ECU is the small relay inside the right engine fuse box ( small # 9 ) . You can swap this one with the one in the left engine fuse box as the left in reality only runs your horn .

This right relay may not be getting the command ground to close and also may be intermittent so you might put your finger on it to ensure it clicks on key rotation

You need this power at the ECU so the ECU can command to close the fuel pump relay in the initial 4 second fuel line priming

 

Xalty has correctly pointed out that car runs normally on pump 1, it should start and continue running on pump 1.
Pump 2 is controlled by the Fuel pump control module (Part DBC12504) and only starts operating at 4000rpm and cuts back off once revs reduce to 3200rpm. Both pumps operate once revs increase over 4000rpm.
I have attached description of the fuel delivery system and a small modification I have made to alleviate problem if fuel pump 1 fails.
Your problem appears to be with perhaps pump 1 relay itself or connections including ground signal from ECM.

John Herbert
1996 XJR

 

John and Parker 2 thanks for your replies.
Seems the problem is no feed to relay 1 when cranking only when ignition on for a couple of seconds. I have rigged an ignition fed relay to switch pump 2 (by-passing relay 2 contacts) just to get me going.
See below what I have attempted.

TEST PROCEDURE to date
*ALL relays still in place.1. Test Fuel Pressure at Fuel Rail entry - Ignition ON

& note pressure. = Shows 5 bar

2. Test Pressure at Regulator Output (return to tank) Ignition ON = Shows 5 bar

drops slightly to 4.5 bar.

3. Remove Gauge reconnect Regulator & attempt to start car. = No Start

4. Remove pump 2 relay and bridge relay contacts & attempt to start car. = Starts & Runs

5. Road test = All OK

I do not have n in line gauge..

Could it be that there is no signal to Relay 1 on cranking, this is strange (to me at least) as car seems to run fine (when relay 2 is bridged) Rev Counter Etc. all looking good so Crank Sensor is OK?

Have bench tested all relays with a 10 Watt Load and all Fuel associated fuses checked

No MIL light on and No Codes stored.

Baffled and been going round in circles guess I have lost the plot and the will to live.

ALL HELP WELCOME

Dave

 

John and Parker 2 thanks for your replies.
Seems the problem is no feed to relay 1 when cranking, ONLY when ignition on for a couple of seconds. I have rigged an ignition fed relay to switch pump 2 (by-passing relay 2 contacts) just to get me going.
See below what I have attempted.
TEST PROCEDURE to date
*ALL relays still in place.1. Test Fuel Pressure at Fuel Rail entry - Ignition ON

& note pressure. = Shows 5 bar

2. Test Pressure at Regulator Output (return to tank) Ignition ON = Shows 5 bar

drops slightly to 4.5 bar.

3. Remove Gauge reconnect Regulator & attempt to start car. = No Start

4. Remove pump 2 relay and bridge relay contacts & attempt to start car. = Starts & Runs

5. Road test = All OK

I do not have n in line gauge..

Could it be that there is no signal to Relay 1 on cranking, this is strange (to me at least) as car seems to run fine (when relay 2 is bridged) Rev Counter Etc. all looking good so Crank Sensor is OK?

Have bench tested all relays with a 10 Watt Load and all Fuel associated fuses checked

No MIL light on and No Codes stored.

Baffled and been going round in circles guess I have lost the plot and the will to live.

ALL HELP WELCOME

Dave

 

Have you bridged / jumperd the # 1 fuel pump relay 30 to 87 like you did # 2 ?




Reset the Inertia / Crash switch , this is a pic from a right hand steering / pedal model and the switch is fwd of the ECU which is under a small cover

There is a rubber cap on top of the button




This does not always reset so you can remove the connector and jumper with a paper clip between the 2 white wires leaving the black wire alone

You are totally bypassing this safety feature by jumpering the # 2 fuel pump relay

See page 60

http://www.jagrepair.com/images/Training%20Guides/801S%20-%202000.pdf

Note : There is a way to rewire the # 1 fuel pump relay to make it work without the factory wiring safety features , it was a clever " work around " and straight forward but twisted wires only worked so long

It was how my my # 1 fuel pump relay was wired as I received the car and worked up to the point of poor worksmanship of the previews owner

Back to the original factory wiring :

The Crankshaft position sensor single signal can continue to be read well enough to give you the tachometer and ignition timing but not well enough to give you fuel pump enable

This failure will give you no CEL code # P0335 as it doesn't always show

This Crankshaft position sensor is reverted to and used in the later half of the starting sequence

In the beginning of starter rotation the different Camshaft position sensor is used for ignition timing only

This starts the car easier and faster as it is more precise in it sees each cylinder top dead center position instead of when the Crankshaft only sees the # 1 as the target comes around

If the Camshaft position sensor is not working ( CEL # P0340 ) it takes more engine rotations for the ECU to determain by the Cramkshaft position sensor which of the 2 engine revolutions is the true # 1 TDC of compression to combustion stroke otherwise it would be # 1 TDC of the exhaust to intake stroke

The crankshaft will rotate 2 turns for each camshaft rotation on a 4 stroke engine

This uses up tour initial 4 second fuel line prime the the key rotation gave you until the Crankshaft position sensor can turn the fuel pump back on

By jumpering The # 2 fuel pump relay and the engine starting it proves you do not have a bore wash condition ( at least not fully ) but you are not using the Crankshaft potion sensor to pick the fuel line pressure back up to where needed

Do you have a Andy Bracket on the Crankshaft position sensor that is not adjusted correctly ?

Is the Camshaft position sensor adjusted correctly ?

Editing , this gets confusing as things switch back and forth and the ability to explain it

 

As has been described already, the second fuel pump normally only comes in to action to provide additional fuel at higher rpm (where the fuel consumption is so prodigious that a single pump can't cope!). The fact that you can jump it and the car runs is a major bonus, and helps to rule out a number of potential causes, again, as has already been described.
The 5 bar fuel pressure you have recorded does seem odd by virtue of being excessively high. It also seems odd as you say you measured it at the regulator output; there should not be any pressure at the regulator output, as the output is the return line to the tank which should flow relatively freely. It is only the input to the regulator which should show pressure, showing that the regulator is doing its job and building pressure in the fuel rail to meet the demands of the injectors.
Turning to your pump 1 problem, if you can hear it running when you turn the key, then I would be inclined to jump it in the same way as you did with pump 2 (having first un-jumped pump 2 obviously) to see whether normal running can be established. My own guess is that the pump will run, but the engine wont, as my hunch is that the feed pipe has become disconnected in the tank.
Another way to progress would be to connect pump 2 to the pump 1 connections to see whether the engine will run. This would prove the pump 1 electrical "side" and would give you a means to get the car moving (just stay off kickdown!)

 

Firstly apologies for the delay in my reply but I have been unwell, slowly on the mend and will be able to resume work on my car soon I hope.

 

Firstly apologies for the delay in my reply but I have been unwell, slowly on the mend and will be able to resume work on my car soon I hope.
As soon as I can will get back to you with results meantime I have not been using the car.
Thanks so much for your very valuable help to date.
Dave

 

I do not own an xj 6
however
I think to leave the 2nd pump business alone as previously said it is only used to get extra fuel to deliver at 4000 + rpm
I would say the fault is in pump 1 as it primes the same as my xj8 then after the engine starts it runs so I would assume your to do the same
first I would jumper 30 & 87 see if there is power at the #1 pump or hear it running
if not well its power to the relay problem
if ok then you will have to look at the control circuit for the relay
the floor safety sw I have heard being a problem B4
I wish you a speedy recovery and good health
regards Dutchy

 

Jumpering the # 1 relay from 30 to 87 gets you off the side of the road or out of someones garage

It's also a confidence booster during a period of defeat

Later manufactured relays are marked 3 to 5

 

Yes I was using the relay base numbers that are on my xj8 as that is where you would be doing the bridge
the relay's themselves have 1,2,3,5 on them in my car
anyway I do wish you well and am interested to see the fault rectified
keep in touch Dutchy

 

Can someone help me with the locations of the fuel pump #1 relay, and fuel pump #2 relay. My car bogs down at higher RPMs. Also shows a MAF sensor issue.

 

Your MAF sensor on the middle wire will read 1.2 volts DC at the proper idle speed to let you know it is alive , volts will climb on throttle up and max out around 5 0 volts

The face of the CKPS can be dirty effecting the # 2 fuel pump enable at higher RPMs

There are 2 different MAF sensors between the normally aspirated and supercharged inline 6 / AJ16 engines