2.5 M51 poor starting hot or cold

Mine smokes when floored and cold. I suspect they all do.

The start issues smell of timing issue as I think others have said. What's the serial number of the FIP?

Grrrrrr said:

Mine smokes when floored and cold. I suspect they all do.

The start issues smell of timing issue as I think others have said. What's the serial number of the FIP?

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There's a bunch of numbers on it. Which one is the serial number?

landyboots said:

There's a bunch of numbers on it. Which one is the serial number?

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Can you take a picture?

wammers said:

The diesel lift pump does pressurise the injection pump to some extent although not very much. It basically just supplies fuel to the internal high pressure pump. The injection pump has an high pressure pump within it to provide pre injection pressure and timing adjustments subject to RPM, controlled by a pressure relief valve. Any excess fuel flowing through the pressure relief valve is returned to the inlet side of the high pressure pump. Spill from the injectors and overflow from the injection pump returns to the tank via the overflow restrictor on top of the pump. Internal pressure will bleed away when the engine is stopped via the overflow restrictor, back to the tank. So without seeing what you have and not knowing how it is set up i would think your lift pump is the problem. Fuel at a minimum rate MUST be supplied to the inlet on the injection pump. And any spill off or return to the tank MUST be from the flow restrictor on top of the injection pump. Essentially giving a fuel circuit from the tank to the injection pump and back to the tank via the overflow on the injection pump. Any other set up will give problems.

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Wammers..... Can you confirm if the P38's in tank pump runs at 3 Bar. Can you also confirm if pressure is maintained on the inlet side after the engine is shut down. I know that the flow restrictor dumps residual pressure at the leak off side but, the inlet side shouldn't be affected by that?

Cheers for your help.

No more than 0,5 bar on diesel.
3 bar pump will add 3 bar to the internal injection pump case pressure messing injection timing.
Been there(with aftermarket eurospare pump dedicated to diesel), seen it on manometer, a bit strange when you see over 12-13 bar at high revs. Too much pressure can crack top cover.

landyboots said:

Wammers..... Can you confirm if the P38's in tank pump runs at 3 Bar. Can you also confirm if pressure is maintained on the inlet side after the engine is shut down. I know that the flow restrictor dumps residual pressure at the leak off side but, the inlet side shouldn't be affected by that?

Cheers for your help.

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Nothing like 3 bars it is a lift pump that feeds a minimum flow rate to the injection pump it does not pressurise it. The Internal high pressure pump produces pressure between 3.5 and 4.5 bars dependent on RPM. Anything above 4.5 bars is vented through a relief valve and returned to the high pressure pump inlet. Meanwhile fuel is constantly returned to tank via the restrictor outlet on top of the injection pump. On your injection pump the internal pressure also depresses a sprung timing device that alters point of injection subject to RPM. Initial static timing on your pump is around 1.54 mm lift on the cam at TDC giving an advanced state for starting with low internal pressure. This timing alters with RPM and internal pressure build to move the timing point of injection towards TDC at high RPMs.

wammers said:

Nothing like 3 bars it is a lift pump that feeds a minimum flow rate to the injection pump it does not pressurise it. The Internal high pressure pump produces pressure between 3.5 and 4.5 bars dependent on RPM. Anything above 4.5 bars is vented through a relief valve and returned to the high pressure pump inlet. Meanwhile fuel is constantly returned to tank via the restrictor outlet on top of the injection pump. On your injection pump the internal pressure also depresses a sprung timing device that alters point of injection subject to RPM. Initial static timing on your pump is around 1.54 mm lift on the cam at TDC giving an advanced state for starting with low internal pressure. This timing alters with RPM and internal pressure build to move the timing point of injection towards TDC at high RPMs.

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Thanks Wammers. I just presumed that once the ignition was switched off that the residual pressure generated by the lift pump would be held in the system until the next startup process but, I'm starting to understand that the FIP wont allow this as it takes whatever the lift pump gives it and dumps off the surplus on the spill side thus leaving no pressure on the inlet side. It's all about flow rate and not pressure so, I will check to see what flow rate the V8 petrol electric pump is physically putting out and compare it to the official as new specs and work from there. I do know that those lift pumps are designed to allow flowback to the tank once they are de-energized. I suspect I could have some vacuum when starting as the fuel lines will be empty from the NRV in the hand primer, all the way back to the lift pump.

Just a quick progress update. I checked the electric lift pump and it is functioning properly and delivering approximately 200ml/per 10 seconds of fuel. I have put a clear rubber pipe between the filter and FIP to check for air bubbles in fuel and it is clear. I removed the inlet manifold and then removed the glow plugs and bench tested them. They are Britpart as far as I remember and take approximately 10 seconds before they begin to glow at the tip and 20 seconds to reach full glow along the full shaft. Do Bosch, NGK, Delphi etc reach their peak glow faster? I replaced them all and connected the fully charged battery and cranked it over after giving it 30 seconds of heat. It cranked for approximately 5 seconds before firing up and running perfectly with no smoke at idle and black smoke on blipping the throttle. I let it warm up and thought I'd try a hotstart. Turned it off and immediately tried cranking it again but it just struggled to crank like as if the battery was discharged. Tried it again after a couple of seconds and it was the same, cranking really slowly. I gave up and went to disconnect the battery and noticed that the positive lead was very hot so it was drawing lots of amps. After thinking about it for a minute, it has always been an erratic cranker and now believe that this may be my problem. How fast should an M51 crank?. If I need to get a starter, are all M51 starters interchangeable?.....

Thanks guys.

BERU glow plugs are white hot after 5 second.
Check voltage loss between engine and negative battery terminal, anything over 0,01V is too much. Replace or add new earth strap with thicker wire, stock is very bad quality and cleaning it will not help.

N2O said:

BERU glow plugs are white hot after 5 second.
Check voltage loss between engine and negative battery terminal, anything over 0,01V is too much. Replace or add new earth strap with thicker wire, stock is very bad quality and cleaning it will not help.

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+1. The glows aren't on that long unless seriously cold outside. Don't fit Britpart glows. They really are utter sh!te.

Remove and clean battery terminal clamps. Slacken negative terminal but do not remove, switch ignition on and off. remove negative terminal within 17 seconds. Then remove positive. Clean battery terminals. Remove and clean and refit terminals to starter motor. Charge battery. Refit battery terminals positive first negative second, and see what you get. Engine should spin quite quickly and start. Have you thought that the battery maybe on it's way home. If it started cold then was slow to crank hot maybe you would like to check charge rate. With 12 volts to them glows should be hot within a couple of seconds.

N2O said:

BERU glow plugs are white hot after 5 second.
Check voltage loss between engine and negative battery terminal, anything over 0,01V is too much. Replace or add new earth strap with thicker wire, stock is very bad quality and cleaning it will not help.

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Thanks N20....I will check all the earth connections and check for voltage drop as you said. Do you know anything about the Bosch Duraterm glowplugs. They promise super fast heat up and durability and are reasonably priced?

Grrrrrr said:

+1. The glows aren't on that long unless seriously cold outside. Don't fit Britpart glows. They really are utter sh!te.

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I'm not using a timer at the moment until I establish what is causing my starting woes. I've been putting on the glows for minimum 30 seconds....

wammers said:

Remove and clean battery terminal clamps. Slacken negative terminal but do not remove, switch ignition on and off. remove negative terminal within 17 seconds. Then remove positive. Clean battery terminals. Remove and clean and refit terminals to starter motor. Charge battery. Refit battery terminals positive first negative second, and see what you get. Engine should spin quite quickly and start. Have you thought that the battery maybe on it's way home. If it started cold then was slow to crank hot maybe you would like to check charge rate. With 12 volts to them glows should be hot within a couple of seconds.

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Thanks Wammers. I will do all that with battery and starter leads shortly. The battery is good. Optima red top. I have two connected to help with cranking. The previous owner created this setup but it seems to draw off of one side only. The positive gets very hot on the offside battery and the negative gets warm on the nearside battery.....

landyboots said:

Thanks Wammers. I will do all that with battery and starter leads shortly. The battery is good. Optima red top. I have two connected to help with cranking. The previous owner created this setup but it seems to draw off of one side only. The positive gets very hot on the offside battery and the negative gets warm on the nearside battery.....

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Clean all terminals and earth points then sounds like you have bad connections or poor ground path. You may need to run a clean ground from engine to chassis.

wammers said:

Clean all terminals and earth points then sounds like you have bad connections or poor ground path. You may need to run a clean ground from engine to chassis.

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Okay....Cleaned all contacts on the starter and it's terminals. Removed and cleaned two earths at front shock absorber turrets and 2 battery to engine straps as well as a big chassis earth strap(seems like some previous owner went a bit overboard ) Cleaned battery terminals and fitted battery. Gave it 20 seconds on the Glow plugs and cranked it. It spun over much better and fired after 4-5 seconds. I Let it warm up and shut it down. Tried an immediate restart and it cranked over very well for 2-3 seconds and fired again. No exhaust smoke at idle but, black when revved modestly. So, I will fit high end rapid glowing plugs and have the static timing done and I suspect, all should be well. Thanks for all the expert knowledge guys. Yous know your stuff

landyboots said:

Thanks N20....I will check all the earth connections and check for voltage drop as you said. Do you know anything about the Bosch Duraterm glowplugs. They promise super fast heat up and durability and are reasonably priced?

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Bosch needs twice the time to reach the same temperature, tested it few years ago.

Mine with beru plugs and bigger pump element starts with first turn even at -18 deg Celcius and 80% timing modulation - too lazy to correct it.

N2O said:

Bosch needs twice the time to reach the same temperature, tested it few years ago.

Mine with beru plugs and bigger pump element starts with first turn even at -18 deg Celcius and 80% timing modulation - too lazy to correct it.

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What is this bigger pump element of which you speak?

wammers said:

What is this bigger pump element of which you speak?

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+1.

Fuel heater?

11mm zexel pump head(M51 is 10mm) from Nissan patrol y61 2,8 td6 (RD28ETi). Theoretically gives 21% more fuel at all conditions.
New from BOSCH/ZEXEL is stupidly cheap(around 100 Euro retail price).