Yesterday I purchased a XJR6 Project. This car has been for sale and sold three times in the last three months. With everyone stating the same issue. 'Needs a new Mass Air Flow Sensor'..

Well, the only reason i purchased was because the price was right for me to play around! This is what I have figured out so far.

Yes, the car idles rough if the MAF is plugged in, but it idles smooth if you unplug it, but there is a serious lack of power, but the car runs very very smooth. There is a MAF code.

So after it running for a long time, i realized there is no supercharger whine, but there is a supercharger there and it's connected up. So I think the supercharger is dead! And this is not a MAF issue, but air is not passing thru at correct amount. It does be more responsive at 3/4 throttle, but very slow response at full Throttle.

Just looking for help, anything to test to see if it's the supercharger? What do I need to do? Thanks All.

 

Supercharger MAF # LNA1620AA

The MAF will read 1.2 volts DC on the middle wire while still plugged in and the proper idle speed

On the perceive lack of supercharger suggest do a harmonic balancer check

you will have the 3rd pully but the same test , after loading up the alternator , A/C compressor the marks should stay lined up after engine shut down

 

So I recall one of the previous owners did the Harmonic Balance thing, but he could of done it wrong? Thanks for your help.

 

See above pic and easy recheck to cover the base

 

If the air is being compressed the blower out will be warmer , you can pull the intercooler coolant pump fuse to feel it being warmed up by compression better

If the compression is being blead off / bypassed the air temp will return close to ambient

See page 55

jagrepair.com/images/Training Guides/801S - 2000.pdf

 

Your supercharged version has a second fuel pump that does not come on until 4000 and turns back off after passing this point down at 3200

You can test the pump by jumper Ing the # 2 fuel pump relay fwd of the battery by itself which is different than the # 1 relay aft of the battery

jumper between sockets 3 to 5




Not sure if a good idea to start the car with the # 2 relay jumpered but only if you have the # 1 relay removed ( overfueling )

If the car will not start after a certain point it will turn on the # 2 fuel pump , so I have read from others

 

Thanks for everyone's Help. I spoke to an owner who had the car for a while, (three Owners Back) as I had his contact when I wanted to purchase the car several months ago. Thankfully I waited and paid a lot less!

So there is a couple interesting things. He said he replaced the Harmonic Balancer, and that he replace the MAF, he then said when he replaced it went again. My Theory is as follows,

1.The car engine runs smooth / But lacks power, and when at full throttle 'Bogs Down'. I think Lack of air getting to the Engine.
2. If the Air is not going through the supercharger at the desired speed, it will back up so to speak into the MAF?
3. There is ZERO Supercharger Whine
4. So....I think I need to remove the supercharger. How do I do this? And does any Eaton M90 Supercharger work on this car?

Appreciate the help in restoring this car!

 

Propper MAF # LNA1620AA

Check for 1.2 volts DC at idle on the middle wire to see if MAF is alive

Harmonic balancer marking recheck

2nd fuel pump check by jumpering relay as well as jumpering # 1

Eaton M60 or M90 has been done by others . I don't have the supercharger version

There is also changing the pully diameter and increasing the intercooler coolant flow

 

I am beginning to think it could be fuel pump related as the engine. Loses power at the higher RPMS. Where the 2nd fuel pump should kick on. Can anyone help me where the fuel pump #1 relay is and Fuel Pump number 2 relay is located? Thanks so much.

 

The # 1 fuel pump relay is in the tray aft of the battery and the # 2 is fwd of the battery by itself

You can jumper from socket 3 ( power ) to 5 which leads to the pump in both relays




A fault of the CKPS is at higher RPMs the square sign wave can not be discerned as well as the pulse groups are closer together

Your fuel pumps are enabled by the CKPS though the ECU

the fuel pump relays are controlled by providing a ground on the control half of the relay at socket # 2

this can be grime on the face of the CKPS other than the connector

As a fuel pump motor fails it will burn the power contacts inside the relay and burn the connector on the pump

you can inspect the connector and replace which some have from reading and swap the fuel pump relay before digging it out

Both fuel pumps use the same control and separate larger power fuse which is # 7 / 30 amp trunk fuse box ' this # 7 fuse is hot at all times

 

So what I did this morning it started right up with fuel pump #2 wired between the same points. The disconnected two, it started right up with Fuel pump #1.

So both fuel pumps seem to work. Im baffled!

 

Also the supercharger does turn. It's not siezed. My mind goes back to that being the only issue tho.

 

Your concern at this point in time is the higher RPMs so give the CKPS a test at higher RPMs

You could have a bad relay originally in the # 2 position

The fuel being consumed rate at idle would be lower than at higher RPMs

You could have a underperforming fuel pump in either position showing up later at higher RPMs

 

I removed relay #2 and #1 around. The car started perfect. I appreciate your help Parker. Thank You. As I mentioned I am a simple mechanic! I'm learning as I go.

 

the supercharger crankshaft pully can be marked with white paint stripes , run the engine and load up the pulley's with the AC compressor and electrical load cabin blower fans running

Stop the engine and the pully marks should line back up

the rubber compound inside the harmonic balancer can be failing not holding the pulleys together, the compound lets the pulleys give a little bit from each other but will line back up

glazed supercharger belt ?

You can leave the belts on and you will have the 3rd supercharger pully