YANST (Yet Another No Start Thread) - fuel pump circuit issues - Defender Source
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  #1  
Old July 26th, 2009, 04:43 PM
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YANST (Yet Another No Start Thread) - fuel pump circuit issues

I've has this problem for a few weeks but have not had time to troubleshoot. I finally got time to work on this today and here is what I found.

First, the symptoms are that is started randomly cutting out while driving (and usually seemed to be after a jarr or vibrations from a rutted road), then randomly not starting (but I could come back later and it would start). I am also experiencing a power drain somewhere [2]. When it doesn't start, I'll either get no click from the fuel pump relay or after a few seconds it will click rapidly on and off. This behavior is seemingly random and multiple attempts at trying it would result in different results each time. When doing the rapid clicking the check engine light flickers. All other dash lights come on as expected including the fuel gauge.

I have a new alternator [1], ignition switch and fuel pump relays (black kind but work fine) as well as another 2 brand new relays I have tried as well.

So I did some testing with a multi-meter at the relay plug and here is what I found

#30 thick brown wire has 12V at all times. I found this a bit odd - should this be off when the truck is off?
#87 two white purple wires (one to fuel pump, one to canister purge valve) when I give this 12v the fuel pump runs, so this eliminates that side of the circuit as a problem afaik.
#87a (two orange white wires) got to O2 sensors, not sure how to check these
#86 white red wire to ECU. Seems to be one of the triggers and ok. 0 volts normally, 12v with the key in position 2.
#85 blue purple to ECU. Seems to be another trigger and seems odd. about 0.33V when the truck is off, but when in key position 2 it spikes to 0.5v for the 4 seconds the fuel pump runs. If I remove the relay and try turning the ignition to position 2, I eventually get the random clicking scenario as you can see this voltage fluctuating between 0 and 0.5v

Does anyone have any idea what this could be?

Bad ECU, or bad inputs confusing the ECU? I have had the ECU case open a couple of times to swap the prom (back to original prom though) but I don't believe I could have caused any damage.

Could bad diodes in the alternator be causing this and how would I test? I'm having a hard time believing I have another bad alternator, but it wouldn't shock me if this was the case. But would like to confirm before trying to get it replaced again.

I'm also curious if anyone can confirm that the fuel injectors pumping fuel in those first few seconds is normal behavior. I guess its just not clear to me what controls the injectors - having a hard time believing the relay simply does - i thought the pump would run and something else would fire the injectors. After multiple attempts turning the key to position 2 to try figure out whats wrong I had fuel dripping out of the exhaust manifold joints.

I can't get it to start even when it's in the magical "fuel pump runs when in key position2" but I think because it's flooded at that point, or the intermittent problem is still there (you can't hear the fuel pump as the engine turns over). I have spark.

Any and all help appreciated.

charles
1. Aftermarket alternator from advance auto was humming when off, and thought to be the cause of the power drain. After replacement this one no longer hums when off (but hums with the key in the 2 position).
2. I am still experiencing the power drain randomly but can't pin down the cause. When in this condition there is a very large drain (i forget the amount but very large) and pulling all relays doesn't affect it at all.
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  #2  
Old July 26th, 2009, 09:17 PM
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"I'm also curious if anyone can confirm that the fuel injectors pumping fuel in those first few seconds is normal behavior"

Yes, it fires and then when it hits 600 rpm it picks up the signal from the distributor.

My bet is whatever you primary problem is (likely a short somewhere, probably the shit alternators you keep putting on it as power is unfused to the alternator) has killed your ignition module and that is causing the no start and cutting out.

If you disconnect the alternator, does it still show a drain on the battery?
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  #3  
Old July 26th, 2009, 09:44 PM
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Quote:
Originally Posted by evilfij
"I'm also curious if anyone can confirm that the fuel injectors pumping fuel in those first few seconds is normal behavior"

Yes, it fires and then when it hits 600 rpm it picks up the signal from the distributor.
Aah, ok, thanks.
Quote:
Originally Posted by evilfij
My bet is whatever you primary problem is (likely a short somewhere, probably the shit alternators you keep putting on it as power is unfused to the alternator) has killed your ignition module and that is causing the no start and cutting out.

If you disconnect the alternator, does it still show a drain on the battery?
I'll need to test this, as admittedly I did not try it. I did get as far as thinking about it if it helps

But since I have spark I was thinking the ignition module should be fine no? Mine is not relocated yet either but I've been too cheap to get the relo kit. If I could be assured that was the problem I'd do it. I so want this thing to be drivable and reliable now, but just throwing money at parts doesn't seem prudent, even in desperation.

Also, i saw references to the fuel temperature sender in other threads. IS there a way to test it, or do my symptoms rule that out?

thanks,
charles
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Old July 26th, 2009, 09:52 PM
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Fuel temp sensor is unlikely, you can just disconnect it to remove it from the loop if you think it is suspect.

A bad ignition module can put out very weak spark which will prevent starting but still show spark when tested. A used ignition module is $25 from roverguy or $90 new for a lucas one from him too. Everyone should have a spare and carry it with you. I would be tempted to purchase a used ignition module relocation kit (you would need to buy the distributor to get the pick up I would think) as new they are now over $400.

Also, AB has the fuel injector test light for silly cheap in the most recent catalog. Another thing worth having. edit part number W121 $3.95
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Old July 27th, 2009, 11:26 AM
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Any way you might have put the PROM in upside down? Severe flooding is really hard on an engine. If fuel is gathering at the exhaust, thats really dangerous.

Have seen wet fuel ECUs flood out an engine. Or damaged ECUs w/ bad drivers.

Did you ever replace the ground cables? Are the gound connections at the back of the cylinder head in good shape?

Can you borrow a fuel ECU t see if your no start is cured. Or try your ECU in someone else's truck?

Good Luck
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  #6  
Old July 27th, 2009, 12:51 PM
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Charles - i have my old 3.9 ecu sitting in my garage if you want to borrow. worked well when i pulled it out and swapped in the 4.2 ecu. it is for an auto Disco if that matters though.
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  #7  
Old July 27th, 2009, 01:03 PM
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Quote:
Originally Posted by pendy
Any way you might have put the PROM in upside down?
No chance - i ran this for over 1000 miles without any trouble after swapping the stock prom back in. It did Experience a night out in the rain before it did this trick, so maybe thats it.

Quote:
Originally Posted by pendy
Severe flooding is really hard on an engine. If fuel is gathering at the exhaust, thats really dangerous.
Yeah it didn't sit well with me but to be honest I think I was more worried about hurting the engine than myself
Have seen wet fuel ECUs flood out an engine. Or damaged ECUs w/ bad drivers.
Quote:
Originally Posted by pendy
Did you ever replace the ground cables? Are the gound connections at the back of the cylinder head in good shape?
I definitely made sure the connections were good but don't recall if I actually swapped out the cables. I'll verify and do that, but I'm pretty sure I'm missing the engine/tranny ground that I have seen other vehicles have so will look into that as well. Yeah, yeah, I know I said I'd do this before.

Quote:
Originally Posted by pendy
Can you borrow a fuel ECU t see if your no start is cured. Or try your ECU in someone else's truck?

Good Luck
Looks like I can!

Thanks as always for the advice

Quote:
Originally Posted by Robbie Donaldson
Charles - i have my old 3.9 ecu sitting in my garage if you want to borrow. worked well when i pulled it out and swapped in the 4.2 ecu. it is for an auto Disco if that matters though.
You da man! Yes I'll definitely take you up on this. I'm actually running what is effectively a disco auto driveline anyway I"m crazy busy this week so don't expect to be able to come this wek, but maybe some evening next week? I have family coming into town over the weekend, but might be able to swing by sometime then too. But I'll PM or call.

charles
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Old July 27th, 2009, 01:18 PM
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not a problem. i'll be around. just lemme know.
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  #9  
Old July 30th, 2009, 11:20 AM
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OK, not 100% sure if it's solved, but if it is, then I think it was the ECU.

Yesterday the stars aligned. It was my first "normal" work day in a while freeing up my time to run down to Robbies and borrow his ECU last night. The guy in brown shorts also showed up with my weekly rover parts, amongst them being an ignition module.

I first swapped out the ECU and tried the key to the #2 position a few times and never once got the fuel relay issue - it pumped every time and immediately. A bit unscientific but it "felt" better. Of course at this point it was flooded again so I couldn't start it.

I figured there was no harm replacing the ignition module either way so swapped that out, but the truck was still flooded so I wedged the intake flap open to let it breath over night.

This morning I nipped out to the garage for a bit and gave her a try. Started right up.

I heard a knock so shut her down, drained/replaced the oil and now she's running great. I'm about a quart low so won't be driving it until I can get some more oil and top it off. Jim, should I be concerned about the long term effects of this? Anything else I should do? never ran in over 1K rpm, and for less than a minute. I filled the (new) oil filter with oil as usual before installing.

I guess I'll see if it problem stays away, and maybe then try the old ECU again, although to be honest at this point if it's fixed I'd rather just leave it alone and buy Robbies

Thanks to all for the help, I'll let you know how it holds up.

charles
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Old July 30th, 2009, 03:41 PM
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For what it is worth I had similar but not exactly these problems. After too much work it turned out to be simply a loose connection of a couple of the wires going to the coil couple with a little corrosion. Cleaning and crimping the contacts solved it all. I assume also that you are sure you have the right relay for the fuel pump circuit. As you probably know this also controls the heaters for the oxygen sensors and a "normal" relay will result in a dead battery as the O2 sensors will be on when the truck is off. I ordered the supposedly correct relay from a west coast supplier (no names in public as I am sure it was a legitimate mistake) and had a dead battery the next day. The only one I have found that works is the silver metal and red stripe relay.
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Old July 30th, 2009, 03:48 PM
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No harm should have been done by the gas in the oil other than cleaning out the inside of the engine given how little you ran it. BTW, make sure you don't have a short somewhere. Ignition Modules and ECUs can be killed by them and you may not have resolved the underlying problem even if it currently runs.
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Old July 30th, 2009, 03:55 PM
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Yeah I have no idea if the underlying problem is solved. The problem is it's intermittent/random. The battery didn't drain all week so I might just be in an ok state right now. But I'll check to see if there is any draw tonight and at least take it for a test drive and see how it holds up.

I'm so tired of this problem though. I just want to drive the damn thing. Seems that's a reasonable thing doesn't it?
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Old July 30th, 2009, 04:00 PM
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Quote:
Originally Posted by cgalpin
Yeah I have no idea if the underlying problem is solved. The problem is it's intermittent/random. The battery didn't drain all week so I might just be in an ok state right now. But I'll check to see if there is any draw tonight and at least take it for a test drive and see how it holds up.

I'm so tired of this problem though. I just want to drive the damn thing. Seems that's a reasonable thing doesn't it?
Drive your accord. Wrench on the rover.
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Old July 30th, 2009, 04:07 PM
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The relays do have to be double pull as described. I have seen black subsitutes that were correct but the diagram on the relay cover should show a double pull to the contacts. Not an off/on between contacts.

I can only hope no damage was done to the engine. I would have removed the plugs and spun the engine over when it was obvious to be flooding. You can hydrolock the engine with large quantities of fuel in the combustion chamber as well.

Time will tell. Fingers crossed for you. I agree to use the different ECU for a while. And lets get the ground wires/cables sorted out before the possibility of damaging anther ECU occurs.

Follow-up Post:

I am sure I could sort through this problem in a few hours. Maybe you should get some help with this to make sure it is not going to come back and haunt you?
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  #15  
Old July 30th, 2009, 04:12 PM
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I drive Janey mostly, but that doesn't make this right! And besides, I"d like to be able to drive the D90 while I give Janey some luvin. I'm wasting the prime soft top driving season here.

Jim, these are double pull and pretty sure they are correct (although they are black ones). I'll go over the grounds again, check all connections etc.

charles

Follow-up Post:

Quote:
Originally Posted by pendy
I am sure I could sort through this problem in a few hours. Maybe you should get some help with this to make sure it is not going to come back and haunt you?
With intermittent symptoms? When are you coming to town? :D

I've thought about getting help, but with a combination of needing to get it to a shop when the problem is occurring and then the fact that it may not happen consistently enough might end up in taking a long time to diagnose and fix (meaning expensive around here).

But yeah If the problem persists I'm going to have to seek help. I have put fewer miles on my d90 in 5 years than I have on Janey in 2. It's plain stupid and I have had enough.

charles
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Old July 30th, 2009, 07:54 PM
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You can check all the power and ground circuits pretty easily and rule out a majority of "intermittent problems"

Its somewhat hard to explain to people how to troubleshoot these types of problems as they often short cut the diagnostic part. And outsmart themselves by what they "feel" the problem is.

Let me start with a basic principle to help. Get a head light off the fender or an old one if you have them left from changing one in the past. Get some jumper cables. Attach the light directly to the battery. See how bright it is and take note.

Attach the ground connection to the engine block and the positive lead to the battery positive. Is the light as bright as before? If the light is noticeably dimmer that is called voltage drop. Bad connection or cable is drawing electricity away from the light.

Attach the ground connection to the frame and the Pos+ to the battery. Is the light as bright as hooked to the battery? If so then there is a ground problem between the frame and engine. If not as bright, it is a problem circuit as well.

You can also hook the ground connection to battery and then hook the positive to the starter connection. Is the light as bright as it was hooked directly to the battery. If not you may have a cable or connection problem on the positive cable.

These type tests can be done with a meter but they can make more sense to a novice with the telltale results of a bright or dim light with good or bad connections.

Obviously a headlight draws a lot of current so only test the larger capacity cables with the headlight. A smaller light can be used all the way up to the individual fuses. When you understand the principles after becoming comfortable with this method of testing you can learn to use a meter instead.

Often it is good to write down your results as they happen to keep from second guessing yourself as well. A diary of diagnosis if you will. Since you may not get at the problem in one attempt it is good to have record of earlier results to compare and keep from retracing.
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  #17  
Old July 31st, 2009, 07:24 AM
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Good advise Jim and I promise I'll check them. I might use a foot instead of a meter though. J/K

Here is an example of why at least the draining problem has been tricky to track down. Yesterday I got more oil, topped her off and backed her out of the garage to cleanup. The plan was to give it a test drive taking the girls to dance but I had a few minutes so I pulled the positive battery terminal to see if my power draw while off problem was still there. Sure enough I had a 3 amp draw. Perfect, i could track it down! Except of course not that minute.

So I decided to heed your warning about driving it like this and damaging the replacement parts as well so I pulled it back into the garage so I could work on it there.

When I came back later, there was no draw (ok, 0.1 right after shutoff, then 0.03 once the ECU went to sleep). I tried running it for a few seconds then checking again as few times but never got the draw again.

Anyhoo, hope to make time this weekend to check all this stuff, but at some point I need to focus on getting Janey prepped for NY so this will have to wait if I can't resolve it quickly.

charles
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Old July 31st, 2009, 10:25 PM
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I took a drive this evening to try induce the draw and was successful. I disconnected the exciter wire and the smaller brown wire from the alternator with no change. But the draw went away when I disconnected the large brown wire from the alternator. I will check the wiring diagram but I'm pretty sure that's the end of the circuit that goes back to the positive terminal of the battery via the starter which should rule that wiring out as being the problem (or the load would still be there after disconnecting the alternator). What sucks is this is a replacement of a replacement alternator @@#@@$!.
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Old August 1st, 2009, 05:07 AM
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What about the wiring between the battery and the alternator? What is damaging the alternators?
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  #20  
Old August 1st, 2009, 12:46 PM
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Quote:
Originally Posted by pendy
What about the wiring between the battery and the alternator? What is damaging the alternators?
Yes I don't know if these alternators came bad or are being damaged. Since it's intermittent I'm leaning towards them coming bad (they are cheap rebuilds) but I obviously want to prove that.

I have not had time to check the wires but I will before doing anything else. Don't expect to be able to today, but hopefully tomorrow.

Thanks,
charles
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