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Discussion Starter #1
hi all - not new to rovers but new to forum. 92 classic, 3.8 petrol. got to the top of the ranch last week, bumpy as heck, as usual, rover did it's normal fine job. finished working - no start. spins but just a 2 second catch. figured it was a fuel problem. changed battery, changed spark plugs (after 8 years). still spins fine but won't stay running. changed fuel filter, checked C4 fuse, checked relays (wiggled them since the maintenance manual doesn't give any values to check, felt them click) checked inertia switch - up/down. same deal - if i crank it, it spins and catches for just a second or two. then imediately hit it again, it spins fine, but no catch. let it sit 5 minutes and it will spin and catch for a couple seconds. its acting like fuel is loading the lines to the injectors, but them not maintaining sufficient fuel pressure - (my guess). checked voltage to the fuel pump from the 3 connector harness - it's 5 volts. i'm guessing that's not enough (but again maintenance manual gives no values). schematics show the inertia switch is next in line up from the pump, but if voltage to the pump is supposed to be 12 v not 5, where am i losing my volts? any guesses?

thanks
 

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Can you measure the fuel pressure? (do you have access to a fuel pressure gauge?)

You can also check you are getting fuel delivery by pulling the supply line to the rail off and putting it in a bottle and seeing if you get any fuel pumped in when you turn on the ignition (usual fire hazard precaution
warnings apply).

However it sounds like you are getting some fuel delivery but not maintaining pressure.

Fuel pressure isn't controlled by the fuel pump but by the fuel pressure regulator, so maybe that is faulty.

You could try carefully partially clamping off the return line to see if that helps, to simulate the pressure reg.

A fuel pressure guage will give a definitive answer though.
 

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Hi

I would say the voltage should be the same as battery voltage, not 5 volts.

Here is the fuel system diagram and more.

Fuel system

If I remember correctly there is an earth wire to the chassis from the fuel pump. At least in my '90 Classic (plastic tank). Four wires, three go to plug and one to ground.

Fuel pressure should be around 2.5 Bar ( around 35 psi).
 

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Discussion Starter #4
thanks for the ideas guys. i am still stuck on the voltage issue. if i don't have enough voltage to spin the pump and move the petrol, i can't do a pressure test. i continuity tested the inertia switch - it's fine, i'm now focusing on the fuel pump relay and the f.i. relay - but i have to wait a day or two until the order for the new ones arrive. i kind of feel it is probably the fuel pump relay itself, and not the f.i. relay. i actually got a little shorting between the case of the fuel pump relay and the chassis when removing the f.p. relay. that could account for where my voltage is disappearing.
hopefully i can get it running friday, as we are getting heavy snow warnings, and i'd rather not have to trailer it off the top of the mesa in a blizzard.

nick
 

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Have you tried tracing the voltage back through the circuit to see where the problem might be? Was the fuel pump relay getting hot?

Jonket, i couldn't get the PDF file to work? Might just be me though...

I'd still chuck a gauge on it if you can, but electronics give me headaches anyway.
 

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Discussion Starter #7
hi guys - got one fuel relay this morning - installed it - no joy. second relay arriving friday. (small town - two parts stores - each store's distributor had only one relay in stock) (you get used to it) jonket - the pdf is exactly what i need - clear, illustrated, actual voltage and resistance values - i'm in heaven. i'll take the trailer up tomorrow - the storm is definately arriving. snow level at 8,000 ft we are parked at 8,750. not so much the snow, but expecting 40 mph winds, which makes coming off the hill exciting. i'll let you know what we get to.

nick
 

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I've had this mysterious fuel pump problem in several cars, in an emergency ( stuck in tunnel ) I just jumped it from fuse panel, ran this way for a while until I found a fuse under right side front seat, behind relays, which was not on wire diagram. This worked on one occasion.
 

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theres nothing special about the fuel pump relay? you can just swap it for anotherone?

I have gone through 3 fuel pumps in the last 6 months. 2 on classics. The harness your mesuring 5 volts at - is that the harness which runs along the side of the fuel tank under the car? or the connector ontop of the fuel pump assembly? Not to insult your intelligence, but its not the fuel level line your measuing 5 volts on?

If the pressure regulators had it the car should stutter and run, just it will die if you rev it or put load on it.

Easiest thing to do is unclamp the fuel line and put the ignition into position 2 for a second. If theres fuel comming out you will know. I found the car will sound like its got some fuel even though the pumps not plugged in, and in hot weather I even mangaged to get it to turn over for a few seconds puely on pressure in the tank I guess from expanding fuel.

Sounds like the pumps shot. If you take it apart and it just appears to have a melted connector, replace the pump it will completely fail soon. Both of mine just had melted spade connectors inside the tank on the physical pump.

 

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Discussion Starter #11
guys - jonket: sorry for the delay, we end up living between storms over here. got the rover off the mesa "on a trailer". the good news is the trailer only tried to pass me three times - i wish they'd use a turn indicator. 14 ft dirt road, 400 ft drop off the left side. we made it.
diagnostics - with a fresh battery, the rover will drain the battery overnight (done that twice this week - i'm learning) so the sparking from the relays mentioned earlier is probably a signifiant point. need to finish removing the right seat - i'm guessing that a million miles over wash-board dirt roads has allowed the ecu harness to abraid - therefore the short to ground. just a guess.

i've got to get 250 head of cattle off the hill this week, so the truck is just in the shop - it will wait. i'll post you all later, and thanks very much for the ideas and references.

nick
 
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