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1991 Land Rover Defender D90 3.5 V8 EFI
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Discussion Starter · #1 ·
Background
I recently completed a body-off, nut-and-bolt restoration of a 1991 Land Rover Defender D90 200Tdi. Swapped in a 3.5 V8, LT85 transmission and a Holley MSD Atomic 2.0 EFI fuel injection system. I've had the vehicle for 4 months now and put on about 2500 miles.

Issue
On 4 occasions while highway driving, typically only after 30-45 minutes, the engine just stalls. Just prior to the stall the EFI lcd screen is showing the Air/Fuel Ratio jumping up to 20+ and even 30+, suggesting it's running lean and being starved of fuel. The AFR is typically around 14. I then wait by the side of the road for 30-45 minutes and then I can start back-up and get home.

Seems like the fuel pump may be over-heating do to its location.

See the attached photos for more detail.

  • Photo A is an overview of the under-rh-seat, side-mount 15 gallon/60L fuel tank. It's this model I think.
  • Photo B shows how the fuel hose routes to the fuel pump.
  • Photo C shows the fuel pressure regulator as it's mounted up against the inside wall of the seat box.

Questions
1) See Photo A. Fuel pump is sitting on top of cross-rail, parallel with the bottom of tank (but not below the tank). Is this probably ok?

2) See Photo B. Hose line goes from draw tube on top of fuel tank then takes a 180 degree turn before it swings back around into the fuel pump. This run of hose line is also about 30 inches/75 cm long. Is this 180 degree turn and/or long hose run causing the overheating? How should it be routed instead? Should I go with an in-tank fuel pump instead? Which one? Or, do I need to stick with an in-line fuel pump with this type of tank/vehicle? Bottom line, is fuel pump likely causing my stalling issue and how should the efi fuel pump best be routed?

3) See Photo C. Is this a good place for the fuel pressure regulator?





 

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The hose routing (photos B and C) and tight loops suggest they could be causing some fuel flow restrictions, which would support your theory of the pump overworking/overheating. Maybe you could make some adjustments there, and possibly use hard fuel lines to prevent this.
Last year, I installed a Holley sniper EFI on my 3.5 and opted for an in-tank pump to replace my OEM low pressure pump. I used Bosch fuel pump 68006 and its fuel strainer 69225 for about $60 online. It mounts in place of your OEM pump on your sending unit inside the tank, keeping the pump cool and providing plenty of pressure at 60+psi. I am not sure if that is an option for you, given your tank style. (mine is on a 110 rear tank).
That said, the holley EFI system did not turn out to be near as reliable and "turn key" as advertised, and I've had some occasional glitches/malfunctions. I'm moving on to diesel..
 

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1991 Land Rover Defender D90 3.5 V8 EFI
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7 Posts
Discussion Starter · #3 ·
Thanks for the input.

1) With an in-tank pump like the Bosch 68006, were you concerned that if the fuel level drops below 1/4:
  • it can cause the draw tube to suck air?
  • without gasoline to surround and cool the pump, will the pump overheat and get damaged?

2) This pump, the in-tank pump for the RRC 1986-1990 and Defender 110 NAS 1993 fits in my D90 side tank, but it's only 35-37 psi of fuel pressure. My Holley MSD Atomic EFI 2.0 needs 60 psi I wonder if there is something similar that can fit in my tank or if this can be modified
 

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You need to verify that your fuel tank is vented properly.
A poorly vented fuel tank will cause all the symptoms you describe.
 

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Thanks for the input.

1) With an in-tank pump like the Bosch 68006, were you concerned that if the fuel level drops below 1/4:
  • it can cause the draw tube to suck air?
  • without gasoline to surround and cool the pump, will the pump overheat and get damaged?

2) This pump, the in-tank pump for the RRC 1986-1990 and Defender 110 NAS 1993 fits in my D90 side tank, but it's only 35-37 psi of fuel pressure. My Holley MSD Atomic EFI 2.0 needs 60 psi I wonder if there is something similar that can fit in my tank or if this can be modified
1) I had no issues at all, this is the same fuel pump as installed in many cars and trucks etc. It does not suck air unless you run it empty or if it is not installed properly in the sending unit. I had no overheating issues, it's the same set up as every other vehicle out there.. The pump is at the bottom of the tank just like the factory set up.

2) I took my old sending unit assembly out of the tank and simply swapped the pumps, which required connecting a hose and a couple of wires. easy swap.
 
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