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ST 2 won't run

2K views 23 replies 10 participants last post by  SS904 
#1 ·
A friends ST 2 will crank over but not fire. There is plenty of clean fuel in the supply line to each throttle body. There is spark to both cylinders and plugs but they are dry, no fuel. There is a wire harness coming off each throttle body, perhaps that is a shutoff valve? What controls it? Any advise?


2016 blinged out PP
2007 Monster S4RS
 
#2 ·
Power going to pump?

Can you guys hear the pump priming when the key is first turned on?

Filter clogged?

If you have compression and spark, all you need is fuel.
.
 
#4 ·
A friends ST 2 will crank over but not fire. There is plenty of clean fuel in the supply line to each throttle body. There is spark to both cylinders and plugs but they are dry, no fuel. There is a wire harness coming off each throttle body, perhaps that is a shutoff valve? What controls it? Any advise?


? I`m a little confused. There is the throttle position sensor on one of the l/h throttle body and a pull cable on the other end. There is also a wire harness connected to each of the injectors which is coloured green. Which harness are you referring to? And there is no shutoff valve, once the ecu stops sending a signal for the injectors to open and the plugs to fire, the engine stops.
 
#5 ·
I was referring to the green ones. But you already answered one of my questions, no shutoff at all. [emoji1303]. I suspect the ECU is not sending the signal to open the injector. Does that sound possible? Any way to test it?


2016 blinged out PP
2007 Monster S4RS
 
#7 ·
A friends ST 2 will crank over but not fire. There is plenty of clean fuel in the supply line to each throttle body. There is spark to both cylinders and plugs but they are dry, no fuel.
Correction, compression, spark, fuel, AND a crank position sensor that is working. They tend to fail suddenly and completely. A quick wipe might help in the short term.
I was assuming Max actually saw the spark based on his statement.

When a CPS quits, the ECU typically won't trigger a spark, because it loses the plot...
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#11 ·
Yup.

I'd check fuel lines in the tank. Particularly the one at the pump's output to the filter. Also, there is a pick up screen at the base of the pump kind of hidden in the pump flange body. It can become clogged, especially if there is some crud in the tank.

If you have spark, then the injectors are also getting power. Power to the injectors, coils and fuel pump comes from a single source. One of the engine management relays. ECU triggers everything independently, however, so you can't necessarily rule out the ECU or the chip. I'd get to those last after being sure the fuel supply chain is good.
 
#13 ·
So the bit of fuel line from the filter to whatever the other plastic housing is was completely disconnected, seems like a likely suspect. Also, the vent lines that run through the inside of the tank are cracked and deteriorating, will replace with new ones.

What IS the second white plastic housing?



2016 blinged out PP
2007 Monster S4RS
 
#16 · (Edited)
That's not how it goes together!!! That fuel/air separator out is just open to the tank. It's the fuel return. I can't tell for sure, but it doesn't look like your fuel pump is even in the circuit. See pic...



And get rid of that plastic filter ASAP. The system has around 40 PSI when operating. No plastic filters. Head to NAPA and grab a 3032 NAPA gold for a couple bucks. Save yourself from the ticking time bomb!:surprise:
 
#22 ·
I too, was very surprised to see the plastic filter in there. And the routing...It's a wonder it ran at all...
 
#23 ·
It didn't run! That was the problem. When I opened it up the line on the filter was disconnected and I guessed it went to the fuel/air separator (I didn't know what it was at the time). Fortunately I got expert advice here on the forum and fixed it. I corrected the improperly routed fuel line, replaced the filter and vent lines and guess what? It runs like s champ! Fired right up.

Thank you for the help guys (specifically SS904 Dan?, and Mike , I really do appreciate it!


2016 blinged out PP
2007 Monster S4RS
 
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