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Discussion Starter · #1 ·
Hey folks. I had Dragon running in August to have its windscreen replaced. No problems indicated or hinted, just needed to be jumped. I have family visiting so I'm trying to get a second car on the road, but when I went to get Dragon out of its garage, it has refused to start.

Now I've been here before and this time I've checked I have power - there is battery voltage to all the EFI and ECU fuses, and according to my ignition tester, there is spark, so this isn't the relay issue I had before. The rest of the symptoms are the same - cranks but won't fire, smell of fuel in the exhaust.

I pulled the spark plugs and all 6 were in bad shape. They're Bosch Super 4s, which have 4 electrodes and should in theory be good for 48k miles, but they showed white deposits and the centre electrodes were worn down by about half. They've been in the engine for about 30k miles. There was also some yellow substance on the plugs - sulphur?

In any case, white deposits means the car has been running hot, so that means running lean. However, I've always thought Dragon runs rich - there's a lot of after-firing after letting off the throttle, and the emissions results showed that hydrocarbons were a little higher than permitted on the latest Euro 4 specs (which Dragon doesn't need to adhere to), and since running rich is better than running lean, I've left it. But seeing the state of the plugs, I clearly need to do something.

Whilst I can smell fuel, I can't tell if the fuel pump is running. I bridged the check connector and put my ear to the tank, but I can't hear anything distinct. There's 12V at the pump connector. I'm wondering if the fuel pump could have been failing over time and has finally died. That said, Dragon has been responsive and still very driveable. I know about the MK2 pumps having a dead-spot issue and my dad says it's been replaced with a MK3 pump instead (Dragon has an in-tank pump). I have spare MK2 pumps but I don't know if they work, though I could hook them up to a battery to test. There are a few kilo-ohms of resistance on the pump terminals in the tank, though I know that's not indicative that the motor works.

Dropping the fuel tank is tedious and I'd like to avoid it. Is there anything else I've missed?

Thanks!
 

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Rob, I would check the EFI fuse under the hood and the power relay in the footwell reset with a paper clip.

Plugs for me ONLY NGKs or Denso, I run the plugs for a 6M per Tanya.

GL
 

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Discussion Starter · #3 ·
Rob, I would check the EFI fuse under the hood and the power relay in the footwell reset with a paper clip.

Plugs for me ONLY NGKs or Denso, I run the plugs for a 6M per Tanya.

GL
I checked that fuse as well, there's 12V to it (and all the fuses I checked are sound). I put an ignition tester on cylinder 3 and it was flashing, so I have spark this time (meaning the ECU should be powered). The tester only confirms there's a circuit and that power is getting to the plug, so it doesn't confirm there is a strong spark.

I know people recommend NGK plugs and I did look at getting them, but my local parts store doesn't stock them any more and did have the Super 4s in stock... then they gave me 2x Super 4s and 4x standard Bosch plugs, getting that resolved tomorrow morning...
 

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Sounds like you are going to be dropping the tank. Only other option is to get a pressure gauge hooked up to the fuel rail and go from there.
 

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There are a few kilo-ohms of resistance on the pump terminals in the tank, though I know that's not indicative that the motor works.
Gargravarr,
I don't have a lot of experience with Mk2 or Mk3 fuel pumps, but from what I've read, the pump resistance should be between 0.1 and 3.0 ohms.
If the resistance across the terminals at the tank are in the kilo-ohms range, I strongly suspect your fuel pump is shot.
If you have other fuel pumps I would measure the resistance on them to compare. If they are under 3 ohms, then I'm pretty comfortable predicting a bad pump.
Dropping a gas tank scares me so I would double check for comparison's sake.

If you are running 14V to the pump and assuming no in-series resistor, the current should be 4.66 Amps which seems reasonable for a fuel pump.
If you are running 14V to the pump and the pump internal resistance is 2 kilo-ohms, the pump will only draw 3 milli-amps.
I'm pretty sure 3 mA isn't going to give much pump pressure.

Again, I would compare what the other fuel pumps measure.

Good luck getting it going

Dale
 

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You can try this. Jump fuel pump check connector and try banging the bottom of fuel tank with the palm of your hand and and listen for fuel pump. It's worked for me on my Frontier pickup and the Supra to get them home years ago. If it starts then it's time for a new fuel pump.
 

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Where is ole dave to show you the fuel tank access hole mod? If you do end up dropping the tank, make sure you cut your floor and install yourself an access hatch for next time. It could be something as silly as low voltage to the pump, but without an easy access hatch you have to drop the tank to find out.

I second the fuel pressure check, it's not hard to do per the TSRM and may save you dropping the tank.
 

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Discussion Starter · #8 ·
Where is ole dave to show you the fuel tank access hole mod? If you do end up dropping the tank, make sure you cut your floor and install yourself an access hatch for next time. It could be something as silly as low voltage to the pump, but without an easy access hatch you have to drop the tank to find out.

I second the fuel pressure check, it's not hard to do per the TSRM and may save you dropping the tank.
No thanks, I'm not cutting holes in Dragon! I've seen those 'mods' and would prefer not to. I've had the tank out a few times already for repairs so it's not difficult, it's just a lot of faffing about with hoses and straps.

It could be something silly, yes, but if it's a dead pump, I'd rather pull the tank out of the car to replace it.
 

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Discussion Starter · #9 ·
Gargravarr,
I don't have a lot of experience with Mk2 or Mk3 fuel pumps, but from what I've read, the pump resistance should be between 0.1 and 3.0 ohms.
If the resistance across the terminals at the tank are in the kilo-ohms range, I strongly suspect your fuel pump is shot.
If you have other fuel pumps I would measure the resistance on them to compare. If they are under 3 ohms, then I'm pretty comfortable predicting a bad pump.
Dropping a gas tank scares me so I would double check for comparison's sake.

If you are running 14V to the pump and assuming no in-series resistor, the current should be 4.66 Amps which seems reasonable for a fuel pump.
If you are running 14V to the pump and the pump internal resistance is 2 kilo-ohms, the pump will only draw 3 milli-amps.
I'm pretty sure 3 mA isn't going to give much pump pressure.

Again, I would compare what the other fuel pumps measure.

Good luck getting it going

Dale
Great info as always, Dale. I'll check my spare pumps. I have a battery and leads to try running them.

I've read that electric motors don't have constant resistance - you can't infer a motor's power draw from the resistance across the terminals, you can only get its wattage by measuring the amps drawn at peak stall. Looked into this when I was modding an electric skateboard (yep!) and needed to know what to spec the electronics for.
 

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An interesting topic.

I suspect that the resistance of the motor doesn't change dramatically. The windings of the armature are copper and while the resistance will increase with temperature and the contact resistance of the graphite brush against the commutator will bounce around with movement, the dramatic change in current draw is due to back emf.

When a coil of copper wire has current running through it, it creates a magnetic field around the wire. When the current through the wire stops, the magnetic field collapses and as the magnetic field crosses through the wire, it induces current flow in the opposite direction. The faster an electric motor spins, the more often the magnetic field is created and collapses. This is called back electromotive force, or emf.

When measuring the resistance of a motor with an Ohm Meter, the motor is not spinning so no back emf is being generated. What you are measuring is the true resistance of the circuit. This will probably measure a reasonably low resistance. As a result when a battery is attached, the inrush current into the motor is quite high, probably in the range of several amps. This is the stall resistance.

When the motor is spinning at speed, the induced back emf effectively creates current flow backwards through the winding. The battery current and the current generated by the back emf are in opposite directions, effectively cancelling each other out. You may have have 5 amps of battery generated current flow and you may have 4 amps of back emf generated current flow with the resultant measured current flow only 1 amp. This appears to be due to a change in resistance, but it is not really. The current draw drop that you measure through the motor is due to back emf, not a change in resistance.

Youtube video on back emf

I don't know how you would measure the resistance of the motor while it is running as a result. You can measure the resistance with the motor not running. You are absolutely correct in that the current draw of the motor will change, but it will drop at speed. For diagnostic purposes I want to measure the static resistance to ensure the brushes and the commutator contacts.

If you measure several kilo ohms resistance with the motor stopped, the inrush current would only be several milli amps. I would expect the resistance with the motor stopped will be 3 ohms or less. If it is not, I suspect the brushes on the motor are worn out.

Now, being a magnificent god of service, I would compare the static resistance of your other motors and compare them to the one in the vehicle. They shouldn't be wildly different. Other things like bad bearings can fail on a pump, but I suspect it will be a brush issue.

Reading what I just wrote reminds me of conversations I used to have with my salesman. I have a diploma of technology and he had a PhD in Chemical Physics. I would ask him about a problem I was having and he would go heavily into the theoretical aspects of the problem, commonly filling a black board with calculations. He would usually say what he thought it was, but then there would be 2 or 3 other things which could cause it as well. Then he would usually say 'well, it really could be anything!'

I go with Dr. Dave. It could be anything! The video above really does remind me of my peddler.

Dale

Oh, and if I'm wrong, oh well.
 

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Discussion Starter · #12 ·
Nope. So my dad and I changed all 6 spark plugs, and I gave the fuel tank a few whacks with a rubber hammer while the check connector was bridged. Still no start. Seems to be pretty conclusive that it's the fuel pump.

What do people recommend to replace the pump with? I've seen the Walbro 255 recommended, and on Raptor Racing, there's a Bosh model 044 offered. I tried both my spare fuel pumps and neither of them showed any continuity, so I think I need to look at a new pump.

If so, anyone know a trustworthy supplier in Europe? I'm wary of fakes on Amazon and eBay.
 

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If you want a trust worthy pump you want an OEM Denso one. Not sure where a reputable dealer is other than the Toyota dealer in Europe though. In the US you can get them from Rockauto and Densos website. You can run the MkIV turbo pump even though its overkill for a 5M.
 
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Yeah get a denso pump if you want quiet and OEM reliability. A 044 requires substantial modification to fit. Walbro 255 is good but noisier than a denso pump and not as reliable.
 

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Post photo of those plugs, eh? White insulators indicate lean condition, but deposits on top of plug surfaces is something else.


Here's some ideas you might want to try before hassle of dropping tank:

1. measure current-draw of pump when it's running. Set multimeter to 10a mode and put it in-line with jumper-connector to see how much power it's drawing... if any. Well, if you can't hear it running, then yeah, it may be dead. Have you tried applying power directly to pump-connector in back? Is that where you measured kilo-ohms resistance?

2. disconnect outlet/return-line from FPR. Attach another hose to FPR-outlet and aim into bucket. Run pump manually and see how much petrol flows.
 

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Discussion Starter · #17 ·
Thanks guys, I didn't figure the OEM pump would still be available. I've phoned a couple of Toyota dealers near me but the Parts guys don't seem to be working today. However having the Denso part number is perfect, thanks very much 82TURBOSUPRA. I'll see if I can source it in the UK.

dannoxyz - yeah, I will. I brushed off the plugs the first time I had them out and I didn't get a picture of the mess on the electrodes. I did test the pump at the connector on top of the tank. Not sure if I have a piece of hose to check for fuel flow.
 

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Discussion Starter · #18 ·
As promised, here's a couple of photos of the plugs. They've been in the engine since 2013, nearly 30k miles. The burn marks around the ceramic are particularly concerning. I brushed off the white and yellow deposits, and I didn't get a photo of them, sorry.
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I managed to get through to Toyota and against the odds, I can get both the Aisin and Denso pumps brand new, however they're asking over £300 for either pump. The Denso pump would need 3 days to ship from Europe, but the Aisin one would have to come from Japan.

I've looked elsewhere and I can get the Denso pump as listed by 82TURBOSUPRA from either eBay or Amazon for much cheaper (£85 from Amazon), but both ship from the US, which entails shipping delays and import taxes. Obviously I don't want to spend huge amounts of money on something as small as a fuel pump, but if the OEM from Toyota is the best option, then I guess I'll have to.
 

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Plugs look OK after cleaning. Burn marks are normal combustion, nothing to worry about. One thing I don't like about Bosch plugs is centre electrode can fall out, causing engine damage. More likely on turbo engines during tuning and getting some knock. I prefer to stay away from them if possible.

What's import-duties when shipped from U.S.? Is it percentage of total declared value or flat-fee?
 

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You could use a walbro 255. The kit for most older Toyotas is the same.
 
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