Champ car quit on the highway,on a bridge,in a very bad spot.Good news,no damage,and nobody was hurt!




Had it towed to my shop at work,and found no power going to the fuel pump!
I tested the relay and found a bad ground on the control side of the relay.
I rigged a temporary ground and made it home,but the car died three times!

I have ordered every part,fuel pump,pressure regulator,filter etc.
Can i bypass the bad ground to the relay,or is there a way to take the ECU apart and fix it's issue?

I do not ever want to be in that situation again!

I removed the tank and got things apart,fairly easy job to do,the fuel pump looks original to the car.
took it apart and it's a walbro!

Now just waiting on the rock to deliver boxes of new goodies!

 

Sorry to hear the news Jim - glad you made it home tho!

Out of my depth on the ground/ecu thing, hopefully someone will chime in soon!

Larry

 

Thanks Larry,while i'm at it I will conquer the damp trunk issue too.I am gonna gut the entire thing,lights,seals,antenna,the whole shebang!

Looking at later wiring schematics,the ground for the controll side of the fuel pump relay appears to go directly to ground.

Watching my meter as I cycle thru key positions,You can see the ground connection going away,all while listening to the dash unit click for the int. lights and timed functions.

Has anyone else had this trouble before?
Cheers all,Jim and Cindy.

 

Hi Jim & Cindy,

Unfortunately I only have the '88 and '93 Electrical Guides, neither of which is exactly right for the '90-'92 cars. I assume the '93 schematic will be closest to your '91, and according to Figure 30, the control circuit of the Fuel Pump Relay and the Fuel Pump itself are both grounded directly to the stud below the right tail lamp/bulb failure module. See photo 6 in the album at the link below:

Welcome to Jag-lovers - Members Photo Viewing Page


On the '93, the Oxygen Sensor Heater Relay is upstream in the same circuit as the Fuel Pump Relay. If that is also true on the '91 it would be worth replacing that relay to see if the situation improves.

On our '93, there is an electrical connector behind the trunk-mounted battery that is in the wiring harness between the Fuel Pump Relay and the Fuel Pump. Either the connector vibrated loose over time or I disturbed it while replacing the battery, and it arced and eventually caused a sudden no-start condition. I don't know if your '91 has this connector but it would be worth checking:

Welcome to Jag-lovers - Members Photo Viewing Page


I don't know how applicable this will be to your car, but the Fuel Pump Circuit Test Procedure at the link below, from my friend and mentor Bryan, has never failed to help me diagnose a fuel pump circuit issue:

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I haven't studied the various circuits that are connected in each key position, but Figures 3 and 6 in the '93 Electrical Guide show the connections that are made and you can follow the page jumpers to see in which positions of the key the Fuel Pump Relay should receive power. I would assume it should receive power in Position II and START, but not in OFF or Position I.

I hope someone reading this has the '90-'92 schematics and can give you some guidance.

Please keep us informed,

Cheers,

Don

 

Wow Don!thank you for the info,It will take me a day or two to sift thru,I am in the middle of a busy work week.Can't wait for the weekend.

I will post more pics as I am proceeding with testing.This is a potentially scary issue!
Together we can figure it out,Thanks again for the leads,Cheers

Jim and Cindy.

 

Well,parts finally arrived,I ordered a Denso pump,opened the box,and found a Walbro! The same pump that has been in the car for 23 years!YEAH BABY!

When I was nursing the car home the pump was making sucking,gurgley type sounds from within the tank.Upon closer inspection of the parts,here is why.

Fuel is not directly sucked up from the tank,but from the inside of the mod can.Fuel is stuffed out the top of the pump,and some is shoved thru a check valve to the engine,and some is directed back to the bottom of the can,thru some kind of DUM-DUM valve that takes care of letting new fuel into the can,and pumped fuel in the mix.The fuel return from the car also is returned into the can.

When the 23 year old DUM-DUM valve fails,the pump sucks the can dry.

THERE IS NO WAY TO FIX IT!I find this UNACCEPTABLE!

Here is the fix I came up with.3/4 inch copper plumbing bits are exactly the same diameter as the sucky-snoot on the pump.Simply make up the extension as shown in the pics,sweat the copper,cool,tin the inside lightly,re-heat and tap the extension onto the new pump and quench quickly.

That sucker is not coming off!

I tapped out the straw in the can and threaded in a screw,blocking the return.Then do the machining,I used a router,but some time with a drill and file might also work.
I also removed the barb from the top of the can,It's pressed in,to service the check valve.I put in a fresh spring,then put it together again with a set screw.

That sucker is not coming off!(but now serviceable)

Now snap the guts all back together.The pump will now obtain fuel from the tank only,and be cooled by the return fuel as normal.

As these cars age,what worked when new,WILL FAIL!
I am not gonna let some 10 cent ungettable part stop the wife from happy motoring!

More to come on this repair yet,Cheers as always,
Jim and Cindy

 

Holy cow - very thoughtful and well done! Thanks for sharing your update with the rest of us.

Scott

 

Hey Jim, if anyone could fix it, you could!

BC ingenuity will always win the day eh?

Keep the updates coming - I might even roll up there to have a gander after I get the new springs in!

btw, I managed to confirm the springs were definitely wrong and have been on the car for at least the last 50,000km - fortunately the new ones are 100% correct so we'll see how she performs on the Jingle Pot again THIS year

all the best

Larry

 

Well,worked on the Champ today,final button-up of the fuel system.
New fuel pressure reg.,fuel filter,bolt the tank in and swar at those damm clips!Should have put them on BEFORE I installed the tank!

I made up a lead wire to ground the control side of the pump relay,I will chase that one down later.I read in the forum somewhere that the ECU controls the ground side,so the pump will not run without the engine running.

Fired her up,and after the air in the system bled out it runs smoooth,and the noisy pump is now whisper quiet!!
The system now works!and with only 4 gallons of gas!

Wife smiles abound!

Beer time!

More pics later,Cheers all,
Jim and Cindy

 

Jim,

An outstanding job and a great display of ingenuity! Thanks for taking the time to photograph your work and upload it for the benefit of the rest of us!

In appreciation,

Don

 

Went for a highway run yesterday and dropped in on Jim and Cindy / took a look at Champ - have to report a super job and boy does that Champ go - like a rocket ship!

We took both cars out on some "quiet" backroads and put them through their paces - while Jim and Cin's car is a bit firmer with the Kyb's than mine (Bilsteins), I'm now convinced (thanks to Jim's objectivity) that my "clunks" are mostly in my imagination or from junk in the trunk and the rear suspension on my rig is just fine!

Anyway a great day of Jag chat and lots of fun to see the passer by's reaction to the sight of two old oyster coloured 40's roaring through the mountain roads!

all the best guys,

Larry

 

Thanks Larry,putting Champ thru paces ,loved having you along!Also loved
rollin`smooth in yours.Nice to bounce experience and details off someone
who has experience.

I am callin fuel issue we had DONE.
Car works well.Happy wife.
Red car has same issue,so more pics,glass re and re,bodywork,tech issues,hopefully documented as we go along.(finally get to MY car)

This will be an issue for our aged cars,and my fix seems to work.

Thanks and Cheers
Jim and Cindy

 

Good job Jim - all done feels good eh?

Made a new three-way vacuum union out of the bronze part you gave me so no vacuum hose slip-off anymore! Thanks a lot!

Onward to Redd!

all the best

Larry

 

Hanging out in the sunshine with two awesome mechanics always makes for a great day, and taking the cars out for a 'show-off' run was the best.
Looking forward to a drive with all three cars one of these days.
Thanks for the company and advice, Lawrence. We'll have to visit your neck of the woods soon.