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Hard starting

6K views 46 replies 10 participants last post by  Hans&Feet 
#1 ·
I have a 2003 1800c. Fresh battery this year. Put new plugs in it yesterday. It has a teclution fi fuel management box. K&n air cleaners. Its became hard to start. Spins over fine just won't start without twisting the throttle alittle. Any suggestions?
 
#5 · (Edited)
You may want to check the fuel pressure regulator (FPR). Internally there is a diaphragm that over time can leak. The diaphragm is vacuum controlled and when you first turn the key and the fuel pump starts to flow fuel to "prime" the system, fuel will leak through the diaphragm into the vacuum line. You will have a flooded engine before you even touch the starter button.


If you have had the bike for 10 years and this has never been replaced, then you should replace it with new as it is just a matter of borrowed time at this point.


One way to check, likely the easiest, is to pull the vacuum line at the FPR and turn the key to prime the system. Any fuel in that vacuum line or exiting the FPR vacuum port indicates you need a new FPR. If you do there's is one more very important thing to know. At this point you have been dumpling a large amount of fuel into your engine, and have washed the cylinder walls with fuel, that is washed off the lubricating film, and have fouled your oil. Check your oil. Does it smell of fuel? You will need to change your oil / filter, use an inexpensive 10W40 oil for this change. Run the bike for 10 or 20 minutes, like a short ride, and then change the oil (no need to change the filter) again with your regular brand. Do this after you have changed the FPR and don't run the engine until the FPR is changed and the fouled oil is dropped and replaced with fresh. The FPR will ship with a rubber plug on the fuel return port. That absolutely needs to be removed upon installation.


Good luck.
 
#4 ·
1. Remove aftermarket fuel manager.
2. Check wiring, vampire clips score strands = poor connection, wires break sometimes.(TPS)
3. Ground fix. FI electronics need a good ground.
4. As Harkon mentioned - FPR, which have been failing since 2013
 
#13 ·
Ok, I got the FPR replaced. Wasnt as bad as I had thought. I replaced the vacuum line which I think was the culprit. But anywho, new FPR, vacuum line, plugs , battery and fresh oil. I think I'm good to go. Bike started great. Will continue to monitor and see. I can tell a difference since I took off that FI tuner. What exactly was that thing supposed to do anyway?
 

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#14 ·
Those are supposed to allow you to tweak the fueling in the low/mid/and high ranges the engine operates in. Basically it's just a pulse stretcher for the injector signal. It's kinda like a jet kit for fuel injection, but it can only add fuel. Mostly, on the VTX, if you add pipes and an air filter for more air flow, it helps to add a bit of fuel in the low end. The VTX is already reasonably rich in the upper range, and handles the mid just fine on it's own ... generally speaking, anyway.


I should add, that a fuel manager, for those bolt ons mentioned, is not necessary for the VTX. Many have done these mods and do not have a fuel manager. Mostly they help with decel pop.
 
#15 ·
I'm still having trouble with it starting some days and other days it fine. I haven't got to ride much since I originally changed the FPR and vacuum line. I took off the vacuum line to see if gas was dripping out and there was none at all. What else could it possibly be? I'm really getting aggravated with this thing. I even checked the fuel vent tube and blew some air through it and it was clogged. Maybe fuel pump or fuel filter?
 
#19 ·
Hard starting part 2

I posted a few weeks back my 2003 vtx1800c was hard to start. With all the advice I got I replaced the plugs, oil change. fuel pressure regulator, vacuum line going to FPR. It's still hard to start. So today I pull off the tank to see if fuel filter and tank had crude in it. It was very very clean. I disassembled the fuel pump assembly and cleaned everything. The fuel filter was not clogged. So I'm lost again and really at wits end with this thing. Could it be possible I bought a new faulty FPR? The tank is still off so I'm still going over all vacuum line and just looking for anything in general. It only has 10k miles. The fuel pump cycles when key is switched on. It just continues to turn over alot before starting. Please help.
 
#31 ·
I posted a few weeks back my 2003 vtx1800c was hard to start. With all the advice I got I replaced the plugs, oil change. fuel pressure regulator, vacuum line going to FPR. It's still hard to start. So today I pull off the tank to see if fuel filter and tank had crude in it. It was very very clean. I disassembled the fuel pump assembly and cleaned everything. The fuel filter was not clogged. So I'm lost again and really at wits end with this thing. Could it be possible I bought a new faulty FPR? The tank is still off so I'm still going over all vacuum line and just looking for anything in general. It only has 10k miles. The fuel pump cycles when key is switched on. It just continues to turn over alot before starting. Please help.
I realize I'm awfully late to the party with this observation, but to me - the very first things to check on a bike that has been sitting for extended periods is - 1) fresh gas, 2) unobstructed air. Maybe it was covered in an earlier thread. But good fresh gas and ensuring their are no accumulations of acorns or nesting materials and other such mischief in your airbox that gets done by rodents and insects is where I'd start. Good luck.
 
#22 ·
Have you done the "Ground Fix"? The early models had a problem where the electrical system grounds to the frame due to corrosion, 2 main points at the coil bolts, and in front of the battery box where all the wiring runs under the tank. I see this point in my head but at the moment it escapes me exactly what it's called, my bad.
 
#24 ·
I checked the 2 pin connector and no signs of burnt wires, corrosion or anything. I checked all 3 grounds as listed on bareass. I sanded and tightened back up. It will be Wednesday or Thursday before I can put tank back in and see what it does. I even unbolted the FPR to make sure I took off the little rubber cap that comes on it off. I checked all the fuses I could find and all were good. This thing is garage kept at all time. I've had it for 10 years and only been in the rain twice. Anything else I can check? What about the fuel pump? It cycles but maybe it's going down slowly. I'm just grasping at straws at this point.
 
#25 · (Edited)
There is a flow test for the FP...

Do you have spark at the plugs when cranking?

Remove camshaft position sensor connector.
Inspect wire terminals. Measure CMP sensor for resistance. It outputs about 10 volts peak to peak voltage..

Do you have a service manual?
Section 5 has info on testing.

Do you have a DMM?
Black/White wire is the +12v feed to FI system.
Test it. It is on the Engine Stop Relay and the Fuel Cutoff Relay.

After market fuel manger?

Remove ECM connectors, inspect, reconnect.
 
#26 ·
I'm just getting a chance to mess with this thing a bit. I haven't got to the cam sensor yet but check to see it it had any codes and it had the number 9 code which says Loose or poor contact on IAT sensor
Open or short circuit in IAT sensor wire
Faulty IAT sensor. Could this possibly be my issue? And my cam sensor is in such a bad spot I dont know if I can even get the connector off of it.
 
#27 ·
Some people have knocked off the sensor washing the X. Only one or two


IAT is open possibly, ECM is confused.
Oxidation on the connector or loose.

Remove inspect, ohm it if you have a DMM.
 
#33 · (Edited)
IAT standard value 1 - 4 K ohms at 68 -86 degrees F
So are you reading 1.7 k ohms and 2.0 k ohms which is within range?
You can also test the IAT from the ECM connectors; Gray/Blue wire to Green/Orange wire.

Next test is voltage test (Ign On) from ECM on Gray/Blue wire to Ground: 4.75 v- 5.25v (Service Manual)

I suggest you test from the Gray/Blue wire to the Green/Orange wire which is the Sensor Ground wire.

Low current devices are subject to oxidation. You should have held up getting a IAT.

Harkon has a download. A different model but all engine parts are the same.
02-03 R/S; 02-04 C
Click on View then you should be able to download.
https://www.dropbox.com/s/k4lqm7s1xs5e00o/Honda VTX1800 RS 02-03 Service Manual ENG.pdf?dl=0
 

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#34 ·
I tested the blue gray wire to ground and it had right at 5 volts. I tested the gray blue gray wire and green orange wire and tested right at 5 volts. I put new sensor in and cleaned my k&n filter and put it back together. It started up fine and took a 20 mile ride. Will let it sit for a couple hours and try again. So wish me luck.
 
#35 ·
Just to update....
Bike it still doing fine. Starting great. So I it was the sensor. I did so much stuff it's hard to say for sure. New plugs, FPR, vacuum lines, clean air filter, ground fix and new IAT sensor. Even pulled the fuel pump out to inspect. That being said I should be good to go for a while. Thank you for all the help and advice. It was truly appreciated more than you know.
 
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