Maxx 470 with Daihatsu dm950G engine

**kevinb** · 08-09-2010, 01:51 AM

Ok. Here is the deal. I have a hydramaster Maxx 470 that has been fairly trouble free for the last 3 years. Today, we started the machine up, and was idling for a few minutes and when I went to turn up the RPM, the machine just died. I never actually pushed the switch to adjust engine speed. So, I cranked the engine over, it sputtered a bit, and wouldn't start.

To back up some, over the last week or so, the machine has died randomly and started right up.

I have bypassed the fuel shutoff solenoid, just in case it was a shut off sensor or relay. I did this bypass with a "hot" wire right from the battery. I have pulled the fuel line off and it appears to be getting a decent flow of fuel from the fuel pump.

I did pull the shutoff solenoid from the bottom of the bowl on the carborator and reinstalled and the machine actually ran for a few seconds before dying. Could this be some sort of carborator problem, fuel pump problem? Electrical problem that I'm just unaware of? I don't know if the machine has some sort of "kill switch" beyond the fuel solenoid.

Tomorrow morning, I plan on replacing the fuel pump, spark plugs and giving it a shot again. What else should I check? If those things don't work, should I pull the carb and clean it? Engine has 2500 hours on it.

**wandwizard** · 08-09-2010, 04:34 AM

Kevin, I would highly suggest calling Jondon service and ask for help trouble shooting the machine. If they are too busy to talk right then they will call you back if you leave a message. I wouldn't replace anything until you talk to someone. You might try to call Hydramaster too. It may be something really simple. I could only guess like throwing darts with a blind fold at what the problem is. If you know where you can get a fuel pressure gauge that will allow you to see if the fuel pressure is high enough. My machine requires a steady pressure of 2 to 3 psi and I found out I was only getting 1 psi. Oddly, my machine had more trouble when idling and always runs fine at full throttle. I did buy a new fuel pump for mine, but have not put it on yet. At 2500 hours I would say your carburetor is due for a good cleaning. I had a lot of problems with mine last December and had it cleaned and rebuilt at a small engine shop. That only helped about 6 months before I started having problems again. I recently decided to just buy a whole new carburetor and it seems to be doing a lot better for now. I can only suggest a few things that won't cost you hardly anything to try.

1. Change your fuel filter if you haven't done that already.
2. If your machine has an oil pressure kill switch on it remove the wire from it and see if the problem goes away. ( Of course make sure you have plenty of oil before you do this!)
3. I'm pretty sure that machine will have a kill wire attached to it somewhere on the side of the engine like mine does. Mine is a yellow wire attached to the right side of the engine about half way down. You may have to call to verify that, but I'm almost certain you will have one. Take the wire loose and see if the engine runs.
4. If you are confident enough about cleaning the carburetor that most likely is called for after that many hours. I had mine done at a small engine shop, but I wish I had went ahead and bought a new carburetor instead of putting a cleaning and rebuild on the old one. I feel that money spent on rebuilding the old carburetor was virtually wasted.

I hope something here I said will help, but I'm no expert and I'm not real familiar with that machine. It does sound like a carburetor problem to me, but I'm just throwing darts. Call Hydramaster or Jondon and see if they can help you troubleshoot the issue.

**kevinb** · 08-09-2010, 08:57 AM

Originally Posted by wandwizard

Kevin, I would highly suggest calling Jondon service and ask for help trouble shooting the machine. If they are too busy to talk right then they will call you back if you leave a message. I wouldn't replace anything until you talk to someone. You might try to call Hydramaster too. It may be something really simple. I could only guess like throwing darts with a blind fold at what the problem is. If you know where you can get a fuel pressure gauge that will allow you to see if the fuel pressure is high enough. My machine requires a steady pressure of 2 to 3 psi and I found out I was only getting 1 psi. Oddly, my machine had more trouble when idling and always runs fine at full throttle. I did buy a new fuel pump for mine, but have not put it on yet. At 2500 hours I would say your carburetor is due for a good cleaning. I had a lot of problems with mine last December and had it cleaned and rebuilt at a small engine shop. That only helped about 6 months before I started having problems again. I recently decided to just buy a whole new carburetor and it seems to be doing a lot better for now. I can only suggest a few things that won't cost you hardly anything to try.

1. Change your fuel filter if you haven't done that already.
2. If your machine has an oil pressure kill switch on it remove the wire from it and see if the problem goes away. ( Of course make sure you have plenty of oil before you do this!)
3. I'm pretty sure that machine will have a kill wire attached to it somewhere on the side of the engine like mine does. Mine is a yellow wire attached to the right side of the engine about half way down. You may have to call to verify that, but I'm almost certain you will have one. Take the wire loose and see if the engine runs.
4. If you are confident enough about cleaning the carburetor that most likely is called for after that many hours. I had mine done at a small engine shop, but I wish I had went ahead and bought a new carburetor instead of putting a cleaning and rebuild on the old one. I feel that money spent on rebuilding the old carburetor was virtually wasted.

I hope something here I said will help, but I'm no expert and I'm not real familiar with that machine. It does sound like a carburetor problem to me, but I'm just throwing darts. Call Hydramaster or Jondon and see if they can help you troubleshoot the issue.

Well, its a 31hp Water Cooled engine. The "killing" of the engine to my knowledge is done with a fuel solenoid on the bottom of the carburetor. Remarkably, this machine does not have an oil pressure kill switch. I've looked all over, and on the brains on the front, there are 3 diodes that connect to the relay. Overheat, Waste Tank, and High Temp.

The first things I did was

1. Override vac tank float(switches go bad, kills machine)
2. Checked for fuel (seemed good, won't even run at the moment)
3. Replaced fuel filter after verifying fuel flow
4. "hot wired" fuel solenoid to open it and override all relays that would shut this valve, thereby killing machine

Tomorrow, I will be giving it a tuneup. Putting on a new fuel pump. I already replaced the filter. If this machine has some sort of other kill switch, or electrical kill to the electrical system, someone please advise me. Thanks!

Kevin

**highmarkschooner** · 08-10-2010, 01:31 AM

have you checked the spark? to determine if this is a fuel problem or electrical you need to check and make sure you have good spark first. if you have good spark and the engine still doesn't run at all then try putting a small amount of fuel or starting fluid directly in the carb throat (be careful of fire) if it runs for a short time then fuel/carb. is your problem. if your fuel pressure is good then you need to clean/inspect carb.

**Jerry** · 08-10-2010, 09:28 PM

Have you checked the oil level? Mine was shutting down and I would have a heck of a time starting up again. I thought it was vapor locking, but it was just a bit low on oil, its real touchy. Could be something real simple like that?QUOTE=highmarkschooner;124580]have you checked the spark? to determine if this is a fuel problem or electrical you need to check and make sure you have good spark first. if you have good spark and the engine still doesn't run at all then try putting a small amount of fuel or starting fluid directly in the carb throat (be careful of fire) if it runs for a short time then fuel/carb. is your problem. if your fuel pressure is good then you need to clean/inspect carb.[/QUOTE]

**kevinb** · 08-10-2010, 11:54 PM

The Maxx 470, stupidly so, was not equipped with an oil pressure kill as part of the engine kill relay system. However, I maintain my equipment very meticulously and don't ever even start a machine without first checking engine oil.

The oil level is adequate.

Here is an update.

I replaced all spark plugs.
Replaced airfilter (was fairly clean since last service)
Pulled carb, there was definitely fuel in the intake.
Checked spark to each cylinder (jumped the tester window very well and very robustly)
Pulled valve cover and all valves appear to travel smoothly. Gaps even looked good since last setting this winter.

I believe we have determined it to be some sort of compression failure. Getting gas, getting spark...just not firing. It did backfire once out the carb.. Possible a head gasket failure between cylinders. Engine never bogged at all under 16" HG load. The machine has burned through coolant a little more than I am comfortable with in the last month and we did burn up a fan belt when the air pump bearing ceased causing the engine heat sensor to shut the machine down, so the loss may have been pressuring out from a leaking head gasket. Worse case scenario, I replace the head. Currently in the process of pulling head (new gasket set on the way).

Wish me luck!