Fuel pump initial operation

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Fridybrydy
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Fuel pump initial operation

Good evening all,

My 2003 K series R300 won't start. Looked like an immobilser fault so had it replaced with a new item. On immobiliser unit replacement car started fine, however next morning back to exactly the same problem. Now from running the car for 6 years I know once the immobiliser has disarmed when I switch the ignition on, I hear the fuel pump run for a second or two and then when I hit the starter button she fires up.

The problem is now, when the immobiliser is disarmed and I switch the ignition on, I no longer hear the fuel pump briefly run and when I press the starter button I only hear a relay click in the MFRU. I say that but on one occasion since the immobiliser replacement, the fuel pump did briefly run and she fired up.

Anyone got any idea's? Thanks in anticipation David

Jonathan Kay
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Private Message sent.

SM25T
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Hi David. Fuse for fuel pump ? Inertia switch needs a press on top to reset ? Is the immobiliser LED extinguished before you press the starter ? Ian
revilla
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Fuel pump is supplied from the main "ECU" 30A fuse, no other fuses in the line. Immobiliser doesn't usually cut the fuel pump on a K in a Caterham (unless the wiring has been modified to be more like a Rover), just stops the ECU firing the injectors. Check the inertia switch as Ian says (push down on too to reset), otherwise could be a wiring fault.

SV VVC 170 - 170.4 bhp @ 7100 rpm - 142.4 ft.lb. @ 4900 rpm

SM25T
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Fuel pump relay in MFRU ?
Wrightpayne
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My car wouldn't start when I built it in '98. Hot wiring the fuel pump and it fired up.

It proved to be a connector in the loom just downstream of the inertia switch in one of the yellow / green wires. It was fixed by Classic Carriage. This year I found the soldered joint which replaced the crimped connector. 
 

I think AnthonyM had a similar issue on his R500. 
 

Perhaps put the ignition on and wriggle the inertia switch loom as it enters the main loom and see if the pump fires into life?

garybee
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No point guessing.  I'd start by checking for power and earth at the fuel pump when the ignition is switched on (as you know it should prime then).  If no earth, fix that.  If no power, work your way back up the system until you find where it's stopping.  Ideally use a test lamp that draws a decent current (headlamp bulb in holder is my choice).  2nd best option is a test light.  Multimeter is poor choice.  No idea what you've already been told by PM so please say if this is just repeating what's already been said.

edit:  I would also suggest you don't start wriggling connections.  If the fault goes away you won't know what fixed it and it will leave you stranded at a later date.

rj
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There's a collection of assembly guides (with wiring diagrams) here:

http://www.caterham.dk/Assembly_Guides

 

tbirds search:

Blatchat Google Search

rkeywood
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Off topic but just quick thanks to rj for the assembly guide link - It's great to have a digitised copy of my 88 guide and a fully legible wiring diagram

R

Fridybrydy
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Thanks for all the reply’s. Had her going yesterday after bypassing the main engine loom to main loom grey connector as this had very intermittent continuity. Then this morning re-taped and re-tywrapped all disturbed wiring in engine bay and behind dash wiring Went to pull her out of the garage and back to exactly same problem with the fuel pump not initially running on ignition on. So frustrating. Basically my car is wired as such. Small connecter at MFRU has green/pink wire that comes from ignition. Checked for 12v when ignition on ok. Black/purple wire is switched to earth via ECU. This operates a relay in the MFRU which switches 12v from a brown/slate wire confirmed at 12v to a green/yellow cable which then goes down to the main/engine loom connected, mentioned above, then back to the cockpit fuse box, through a 10 amp fuse, back out of the cockpit to the inertia switch, though the inertia switch and off t’ fuel pump. Had the MFRU off applied 12v and earth to green/pink and black/purple terminals and the relay operates with continuity observed across brown/slate and green/yellow terminals. Re-fitted and connected MFRU. Broke into wiring, connected 10amp inline fuse and wired from green/yellow wire coming out of MFTU to green/yellow wire going to inertia switch, no joy. Pulled large connector off MFRU and shorted between brown/slate wire and green/yellow wire and fuel pump ran proving wiring though inertia switch to fuel pump ok. Re-connected MTFU, and then monitered for 12v and temporarily fitted in-line fuse. Dis-armed immobiliser, switched ignition on no 12v monitored at inline fuse. To summarise, I’ve had a new immobiliser fitted and the car fired up. Next morning, she wouldn’t start. Just a click. Then bypassed grey connector and she started. Then this morning, as soon as I put the ignition on I knew she wouldn’t start as I didn’t hear the initial running of the fuel pump. I’m now going back out to the garage to try and figure out why the fuel pump relay is no longer energising from the ECU. Any divine inspiration?

Thanks David.  

Fridybrydy
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Update, just plugged everything back in, disarmed immobiliser, ignition on fuel pump had the initial few seconds run, great. Ignition and immobiliser cycled many times all satisfactory with the fuel pump initial run happening. Went and had a sandwich, came back without disturbing anything, disarmed immobiliser, ignition on, fuel pump did not run Aahhhhh. Disconnected and reconnected MFRU both connectors and now back at square one. It is so intermittent. Does anyone know where I can purchase a new MFRU please. Got to swap it out afore I go insane. 

David