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1987 Lotus Esprit rebuild

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I have been working on trying to get this car to run and I'm having trouble w/ getting power to the fuel pumps. I have the book and it looks like there are 7 parts that could be the problem: fuel bypass sped sensing, fuel bypass relay, fuel pump control, B079M6133F, A079M6141F, fuel enrichment module, and fuel pump failure module. I have found 3 of the 7, the first 3 of this list I have and put in but nothing changed. Does anyone know how to trouble shoot this and where can I get parts?

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Old fuel pumps often fail. Even if they pump they might not have enough power to raise enough fuel. For about £40.00 I would get a new one any ways.




"Belief is the enemy of knowing" - Crrow777

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Thanks for the reply. I have already replaced both fuel pumps, the fuel accumulator, and the fuel filter. After replacing them and hooking them up I turned the key on and they didn't run so I hooked up jumper wires direct from the battery to the fuel pumps and they turn on and pump the gas to the carb. There are other issues too because I tried to start the car while I had the jumpers hooked up and it didn't fire so I'm also worried about spark. I figured I should start w/ getting power to the pumps first and then worry about the rest of the issues. I'm guessing it has to be one of the 7 things I mentioned above. Any help?

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Maybe the ignition switch/fuse/wiring has a fault. Check to see where the volts are....get DVM and a wiring diagram and follow the magic lines around, tracing the wiring on the car for the ignition and fuel pump circuits. Changing parts willy nilly doesn't have to systematically diagnose the problem.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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If your car has the brown wire connected to your battery post (forget which polarity), is it frayed, split, corroded, or loose? In another thread, the OP could not start his car, and experienced great consternation, until he realized this wire--which I seem to recall provides power to the fuel pump--was not connected. My '86 HC has it, and I'm going to replace the old, crimped thing with a new 4 gauge wire as I upgrade my alternator.




1986 Esprit HCI (Bosch-injected)

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  • 2 months later...

Check for continuity/voltage at the relay socket terminals. Often, terminals are loose and get pushed down by the relay blades. 

Try to jumper pumps.

Proper connections to jumper pumps at the relay sockets are noted here:
Remove both pump relays. Make two “jumper” wires with spade terminals on each end. Plug one end in the relay socket middle slot towards the front of the car (#30, black wire), and the other end in the slot towards the rear of the car (#87, banded wire). You should jumper the primary pump FIRST (the relay socket to the LEFT), BEFORE you jumper the secondary pump (RIGHT relay socket). Otherwise, or you could actually damage the secondary pump by running it dry.
Keep both pumps running for a minute or two to purge air bubbles from fuel lines.
Pumps should “hum” and stay cold. Any “grinding” noises or complete silence from the primary pump indicates an electrical trouble. If pump blows the 15A fuse – pump may be jammed.

If primary pump does not work efficiently or provide enough fuel to the secondary pump, the latter starts cavitation, which sounds like a “grinding” noise. Listen to each pump with a mechanic’s stethoscope. Primary pump provides the volume and secondary pump provides pressure.
To stop the pumps, disconnect the secondary pump first and the primary after that, or disconnect the positive battery cable. Remove jumper cables, replace relays. Note: Inertia Switch has no effect on this procedure.

Also, if inertia switch or RPM module is bad, pumps won't run.

Edited by MrDangerUS
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