[frankoart]

After sitting many months, when I tried to start my 2008 trx420tm, it clearly had fuel supply problems. It was hard to start but when it did it idled ok, but died when I put it in gear. I let it warm up for a while, then it died and hasn't started again. It backfired once on the first attempt to start it.

The battery is fully charged and new.
I confirmed that I have spark at the spark plug.
I replaced the air filter.

Here's a summary of what I've tried so far.

1. Cleaned fuel pump and replaced fuel filter.
2. Removed tank, cleaned it and replaced a defective fuel tank petcock.
3. Replaced fuel tank and filled with fresh gas.
4. Confirmed that fuel pump works and fuel is flowing to fuel injector.
5. Cleaned and tested fuel injector. It works.
6. Ran continuity and voltage tests that indicated the PGM-FI was defective. I replaced it.

I'm stumped.

The service manual says there should be a beep from the IACV.
I don't hear any beep.
Service Manual Trouble Shooting says to confirm that the IACV is not stuck.
It isn't clear on how to do that.

There is a fast clicking for a second coming from something near the battery when I turn on the key. I think it has always done this. The starter operates perfectly and the fuel pump primes.

I'm sure that the original problem was the fried fuel petcock.
It was completely rotted and destroyed.
After I cleaned the fuel pump and replaced the filter, I determined it wasn't getting fuel from the tank, I tested my work by pouring some gas in the fuel pump. It started and ran smoothly for a few seconds until the fuel was used up. That's the last time it's started.

I suspect that the new starting problem was created when I removed and reinstalled the fuel tank. But, I have no idea what I could have messed up by doing that. It was pretty tight squeeze and it is possible I broke some connection.

 

[retro]

Maybe the petcock assembly you put on it is bad? Is it an OEM Honda part or a china knockoff? I'd retrace steps until you find out where the fuel blockage is... perhaps the hose is clogged too.

 

[alloutdoors]

Are there any associated "fuses" which may be keeping it from firing off? You are sure isn't or is making it to the cylinder head? To check, try starting it a few times and then remove the spark plug to verify fuel is making it that far. If wet from fuel, toss in a new plug may have fouled it out from so many attempts.

 

[frankoart]

Maybe the petcock assembly you put on it is bad? Is it an OEM Honda part or a china knockoff? I'd retrace steps until you find out where the fuel blockage is... perhaps the hose is clogged too.

The fuel petcock works. Fuel is flowing to the fuel pump and all the way to the throttle body.

 

[alloutdoors]

The fuel petcock works. Fuel is flowing to the fuel pump and all the way to the throttle body.

A little of a long-shot, but do you know if fuel is getting in the cylinder head? If you spin it over, you should have a wet plug from not starting and may be worth trying as well as to verify you are still getting adequate spark to fire off.

 

[frankoart]

Are there any associated "fuses" which may be keeping it from firing off? You are sure isn't or is making it to the cylinder head? To check, try starting it a few times and then remove the spark plug to verify fuel is making it that far. If wet from fuel, toss in a new plug may have fouled it out from so many attempts.

I checked all the fuses and they are good – at least the ones under the rear of the seat. Are there any more?

I tested the fuel injector on the bench when I cleaned it by applying power as I sprayed fuel system cleaner through it. It was operating on the bench and the spray pattern looked good.

I'm not sure that the installed fuel injector is firing and that fuel is making it to the cylinder head. Continuity and voltage tests indicated it was getting power at the connector.

I'll pull the spark plug today to see if fuel is making it to the cylinder head. Thanks.

 

[alloutdoors]

Are there any associated "fuses" which may be keeping it from firing off? You are sure isn't or is making it to the cylinder head? To check, try starting it a few times and then remove the spark plug to verify fuel is making it that far. If wet from fuel, toss in a new plug may have fouled it out from so many attempts.

I checked all the fuses and they are good – at least the ones under the rear of the seat. Are there any more?

I tested the fuel injector on the bench when I cleaned it by applying power as I sprayed fuel system cleaner through it. It was operating on the bench and the spray pattern looked good.

I'm not sure that the installed fuel injector is firing and that fuel is making it to the cylinder head. Continuity and voltage tests indicated it was getting power at the connector.

I'll pull the spark plug today to see if fuel is making it to the cylinder head. Thanks.

As mentioned, looking at the cylinder head may be a long shot, but you will have the opportunity to validate if fuel is actually arriving and if not, "potentially" know where to move back to and get it resolved.

 

[frankoart]

As mentioned, looking at the cylinder head may be a long shot, but you will have the opportunity to validate if fuel is actually arriving and if not, "potentially" know where to move back to and get it resolved.

Hey, it's a shot and I'll take it. While I'm at it, I can try the old trick of putting some gas through the spark plug hole to see it that makes it fire.

 

[frankoart]

I removed the spark plug and inspected it.
It looks brand new and wasn't wet with gas.

It was difficult to tell if the cylinder head was wet with gas. I probed with a swab stick and it seemed pretty dry. There is some carbon on the piston head.

I put a little gas in the spark plug hole and replaced the spark plug. When I tried to start, it coughed a few times and fired over a few turns.

That tells me that the ignition system is working but the cylinder is not getting fuel from the fuel injector.

That implies there is a fault to whatever triggers the fuel injector, so I removed the fuel injector and left it connected to the fuel line and its electrical connection. It should squirt fuel when I turn on the ignition key and/or push the start button.

It didn't. So, either the fuel injector is faulty or the circuit that actuates it is faulty. Since the PGM-FI is new, I guess I have to assume there is a short in a wire or connector somewhere.

The IACV spun when I turned on the key. I guess that's what it is supposed to do.

I still don't understand why it quit starting when I removed and replaced the fuel tank. Maybe just coincidence.

 

[retro]

It sounds like a fuel pressure issue. Do you have access to a pressure gauge? The fuel pump/pressure regulator should produce about 50 PSI after turning the ignition switch on and off (fuel pump runs for 2 seconds each time the key is turned on) a few times.

 

[frankoart]

It sounds like a fuel pressure issue. Do you have access to a pressure gauge? The fuel pump/pressure regulator should produce about 50 PSI after turning the ignition switch on and off (fuel pump runs for 2 seconds each time the key is turned on) a few times.

Thanks for the reply, Retro.
I don't have access to a fuel pressure gauge. But, when I removed the fuel injector, fuel sprayed and hissed as the bolts on the injector joint were loosened (I left the fuel line attached). The fuel was under a fair amount of pressure.

There doesn't seem to be any kinks or bends in the fuel line.

I'll see if I can get my hands on a fuel pressure gauge.

 

[retro]

Do you have the sensor in the airbox plugged it each time you try to start it? 420s gotta be plugged in or they won't start/run. I assume that you have already tested and ruled out the Bank Angle Sensor? The Fuel pump/Engine stop relay pair too..?

 

[frankoart]

Do you have the sensor in the airbox plugged it each time you try to start it? 420s gotta be plugged in or they won't start/run. I assume that you have already tested and ruled out the Bank Angle Sensor? The Fuel pump/Engine stop relay pair too..?

The air box sensor (on the right front of the air box) is plugged in.

If the bank angle sensor is mounted to that black plastic plate behind the PGM-FI, that could be the problem. I detached (but didn't unplug) all the modules and removed that plastic mounting plate for access when I removed and installed the PGM-FI. I haven't reattached them yet.

As far as I know I did not monkey with the fuel pump/engine stop relay.
Would the fuel pump run if it was not working?

 

[retro]

There are two relays inside... the fuel pump relay and the engine stop relay. But that probably isn't your problem if the BAS is not mounted onto the bike yet. The BAS shuts the motor down on steep grades and rollovers so if it isn't mounted properly... well, you get the picture... see the attachments.

 

[frankoart]

There are two relays inside... the fuel pump relay and the engine stop relay. But that probably isn't your problem if the BAS is not mounted onto the bike yet. The BAS shuts the motor down on steep grades and rollovers so if it isn't mounted properly... well, you get the picture... see the attachments.

I really appreciate your suggestions, Retro.

There are three modules connected together that mount on the mounting plate. The rest of the things just looked like wire connectors.
I reinstalled all that stuff and it still doesn't start.

I considered that I may have broken some connection when I removed the front fender and fuel tank. The engine stop came to mind. But, if that were the problem, it wouldn't fire when I put fuel in the spark plug hole, would it? It did fire when I did that. All the engine stops I've seen off turn off the ignition – at least on boats and lawn mowers.

I can't find the Bank Angle Sensor. My diagram shows it to be ahead of the battery and up about even with the throttle body on the left side. I don't see anything there – except what looks like a multi-wire connector attached to the frame.
At any rate, that's something I haven't messed with or removed.

 

[retro]

I can't remember for sure... but I think the BAS kills the fuel injection, not the ignition. I'd have to go back through the manual to be sure, but I remember that it doesn't kill everything like you'd assume it would...

I imagine you'll have to retrace your steps, tearing everything back down to find the problem. The FSM shows how to check the BAS and relays.

I've found (in my limited experience) with fuel injection on the early 420 Ranchers, that once the pump sits for a while with rotting fuel in it, its done. I've only worked on a few, but I've had to replace pump assemblies on almost all of them due to pumps seizing up. I'm not saying yours is junk... just that it can sometimes run and pump but still be junk.

 

[frankoart]

I can't remember for sure... but I think the BAS kills the fuel injection, not the ignition. I'd have to go back through the manual to be sure, but I remember that it doesn't kill everything like you'd assume it would...

I imagine you'll have to retrace your steps, tearing everything back down to find the problem. The FSM shows how to check the BAS and relays.

I've found (in my limited experience) with fuel injection on the early 420 Ranchers, that once the pump sits for a while with rotting fuel in it, its done. I've only worked on a few, but I've had to replace pump assemblies on almost all of them due to pumps seizing up. I'm not saying yours is junk... just that it can sometimes run and pump but still be junk.

You are correct. The wiring diagram shows the kill switch is on a positive wire and does kill the fuel injector as well as a few other things. If I need to temporarily disable it, I have to determine if it is on/run and off/stop. It looks like closing it actuates a relay that shuts things down.
It is possible I damaged a connector or wire when removing the front fender and fuel tank, which makes sense as that was when it died.

I've located the position of the engine stop and fuel pump relays, as well as the the BAS. Testing looks pretty straight forward with no special tools required other than probes which I can jury rig.

I can't test them this afternoon as it has started raining again. It should clear up tomorrow so I can get back to it.

Thanks again for all your help. I really appreciate you taking the time to help me with this. I was stumped.

 

[retro]

You are most welcome, and if I am ever any help to anyone at all, I'm pleased! Have fun with it!

 

[frankoart]

I tested the engine stop relay and the fuel pump relay. They both check out.
I'm not very good at reading wiring schematics, but it looks to me that the engine stop switch is linked to both the fuel injector and the ignition coil.

How it shuts them down, I don't see in the schematic.

I think this eliminates the engine stop circuitry since I still have fire.

I should be able to measure current going to the fuel injector connector. I didn't get a result I could interpret the first time I tried. I'm going to try again tomorrow.

I've highlighted the engine stop circuitry on the attachment.

 

[Jeepwm69]

Bank angle sensor is on the bottom of the top frame rail right under your left butt cheek if you're sitting on the seat.

Run a jumper from battery + to red/black wire on the coil. This should bypass any safety features that will cut fuel or spark.

If it still doesn't fire I would guess your fuel pump is toast.

The fuel pumps on 420's are crap. If you leave them sitting long at all with ethanol fuel in them they die.