Does a 3.9 have a govenor at 3400 rpm? - Defender Source
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  #1  
Old November 18th, 2006, 08:31 PM
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Does a 3.9 have a govenor at 3400 rpm?

Hey guys,

I just finished getting my D tuned-up. The last time it was tuned they didn't tighten down the distributer so my timing was screwed as well.

Anyway, I found that in 2nd and 3rd gear, at least (have not tried it in other gears yet) the engine will not surpass 3400 rpm. I initially thought it might be a low fuel pressure issue but it seems to act more like its govenored.

Is this the case or do I need to keep diagnosing? It's a 94 D90 3.9l.

Thanks in advance,
Scott
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  #2  
Old November 18th, 2006, 09:16 PM
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Your truck does not have a 3400 rpm governor. You have some other problem
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Old November 18th, 2006, 09:32 PM
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if you are in neutral and hold the gas on the floor does it still cut out at 3400. I think i would start with the fuel filter, then check the pressure on the fuel rail. what did "they" do for your tune up?
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  #4  
Old November 18th, 2006, 11:34 PM
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I'll try that the neutral check.

I did the tune-up.
New NGK Plugs, new dist. cap, wires, fuel filter, and set the base timing to 6* btdc. I also checked all of the vacuum connections with brake clean and no leaks were found. Air cleaner is only 2 weeks old. I can find no other problems so far. I am idling at ~800rpm. This is at an altitude of 7260'.

I ordered a Repair manual but it has let to show up.

Any ideas? Could a malfunctioning fuel pump cause a consistant cutout at 3400 rpms?
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  #5  
Old November 19th, 2006, 10:35 AM
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Robert Dassler
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Several things to check & be aware of...
*As mentioned, check fuel pressure/volume.
*Make sure your distributor cap & rotor are GENUINE LR parts. Not NAPA, not the discount junk on ebay or from any of the mail order parts suppliers....Genuine parts in a Land Rover box. I have yet to find decent aftermarket caps & rotors anywhere. Yes, the Genuine stuff will cost about $80 but it is worth it and should last 75-100k miles. The aftermarket junk will burn through and arc under load but run mostly ok at idle & light load, potentially giving you the problem you have. Can be a pain to diagnose. Diagnose by substituting known good components.
*Set your timing to 9*BTDC to compensate for altitude
*If the problem still persists I would check the distributor dwell to determine the health of the ignition module. I would also check the firing kV of the coil. A weak ignition coil can also cause problems under load and will do so at about the RPM that you are experiencing the problem. You can also test by substituting a known good coil. Keep in mind that a bad module can damage a coil by overheating it, so you may need both parts if one is bad. Not all coils are the same. Get one for an electronic ignition...should have an internal resistor.
*Check to make sure that the exhaust is not plugged...drop the down pipes and see if it revs freely.
Good luck!
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Old November 19th, 2006, 10:35 AM
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What should the fuel line pressure be? Fuel rail pressure?
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  #7  
Old November 19th, 2006, 10:43 AM
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At your altitude, about 32psi running with the regulator vacuum hose connected, about 36-38psi with the regulator vacuum hose disconnected.
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  #8  
Old November 19th, 2006, 02:37 PM
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Hey Scott if you don't mind me jumping on your thread with my own problems, I wouldnít mind asking a question too. I also have a problem that feels like I have a governor on my truck too.

Itís not a RPM issue, but a speed issue. I can get it up to 90mph, and all the sudden it feels like the gas to the engine is shut off. The truck like stops for a second and then accelerates again. Almost feels like someoneís taking their foot off the gas at such a high speed. Do you think itís the gas just not pushing though fast enough to the engine or a governor? I mean itís not a big deal because 90mph is fast for a Defender, and I rarely go that fast, but when you need to pass someone its kind of a pain in the ass.
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  #9  
Old November 19th, 2006, 02:49 PM
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For what it`s worth, I have the exact same problem (cuts at 3400rpm), but i`m at sea level...? If that makes a shit of difference. Let me know what ends up working for you
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  #10  
Old November 19th, 2006, 03:19 PM
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Quote:
Originally Posted by ini88
Hey Scott if you don't mind me jumping on your thread with my own problems, I wouldnít mind asking a question too. I also have a problem that feels like I have a governor on my truck too.

Itís not a RPM issue, but a speed issue. I can get it up to 90mph, and all the sudden it feels like the gas to the engine is shut off. The truck like stops for a second and then accelerates again. Almost feels like someoneís taking their foot off the gas at such a high speed. Do you think itís the gas just not pushing though fast enough to the engine or a governor? I mean itís not a big deal because 90mph is fast for a Defender, and I rarely go that fast, but when you need to pass someone its kind of a pain in the ass.
you are hitting the governor on the truck. If you want to remove the governor get a disco I cold start chip for the ECU.
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  #11  
Old November 19th, 2006, 04:50 PM
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Well, the saga continues. I set the timing to 9* BTDC and it appears to have no effect. Continues to conk out at 3400 rpm. I can not find a port in which to check the fuel pressure, the rail appears to have none.

Thank you Roadsiderob for all the ideas. I do not have any known good parts as this is the only D I have and have not had it long. I do not have the ability to check the dwell so I will start next with the exhaust and then I guess I will have to take it a shop. The LR dealer is not an option as they are 3 hours away and they are the ones that left the distributer loose to begin with, as well as some other issues.

I will pass on the fix when I find it.

Thank you all. -Scott
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  #12  
Old November 19th, 2006, 05:23 PM
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This thread begs the question (that is most likely answered in the owners manual): what is the redline?
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  #13  
Old November 19th, 2006, 06:56 PM
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The engine is RPM limited to 5500RPM by the ECU. The D90s were speed limited to 90MPH due to the BFG tires speed rating. Speed limiting is done by shutting down injectors as the ECU on the 1994 & 1995 D90s does not have control over the ignition system.
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Old November 19th, 2006, 07:32 PM
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Thanks, Rob -- where does the 3.9 stop making power? I shift at 3K (and have for the last 10 years . . . am I being a girly-man? Have I been missing the bone-rattling fury that occurs above 3K all these years??
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Old November 19th, 2006, 07:50 PM
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nah it seems to fall off around 3 or so. i find between 2 and 3500 is ideal. I opened mine up shifted when it got towards the 5 mark just seems to make alotta fuss and really fall off the power around there.
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  #16  
Old November 19th, 2006, 08:14 PM
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Quote:
Originally Posted by ini88
I can get it up to 90mph, and all the sudden it feels like the gas to the engine is shut off. The truck like stops for a second and then accelerates again.
Daniel, this is your truck politely telling you that you are putting your life in danger driving at 90 in a D



charles
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Old November 19th, 2006, 10:34 PM
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Quote:
Originally Posted by cgalpin
Daniel, this is your truck politely telling you that you are putting your life in danger driving at 90 in a D



charles
you are very right! flipping at that speed is 110% deadly. I should remember im in a D not an STI.
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  #18  
Old November 20th, 2006, 07:58 AM
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A healthy D90 will pull to at least 4500rpm.

Per the guy with the 3400 issue, I would try swapping in a known good ecu as well. You can buy a used one out of a disco I in the 100-150 range.
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  #19  
Old November 20th, 2006, 09:59 AM
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Peak torque is at 3100RPM for the 3.9L, operating the truck between 2000-3500RPM keeps you in the power band. I'll occasionally run to 4500 RPM, rarely above that.
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  #20  
Old November 20th, 2006, 08:23 PM
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Both my 3.9 on a 14CUX ECU, and my 5.0 on a chipped 14CU ECU, have had a definite fade at exactly 3400. It's like the ECU tells the fuel system to operate in a different mode -- it's slight but still there. I thought at first it was the cam on the 3.9, but the brand new 5.0 did the same thing on the old 14CUX and the replacement 14cu.

I rev to 5500, 6000 very occasionally (my custom chip allows for a red line at 6000). But I'm curious if this 3400 rpm hiccup is some kind of sensor going bad, and gone bad if your truck won't exceed those revs...

DW
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