1991 U300-- bought it!

Topic: 1991 U300-- bought it! (Read 7561 times) previous topic - next topic

Re: 1991 U300-- bought it!

Reply #125 – June 09, 2020, 04:06:12 pm

For those 1992, 93, and 94 U300 owners with the air intake behind the rear tires, this is what a NAPA 2610/Wix 42610 looks like after it gets wet. You can see the side by side construction between the two brand in the photos below. the Donaldson DBA5029 construction is far better than the Wix/NAPA filter. We were really lucky it didn't fail and dust the engine.

Let's get the correct air filter part number for the early U300s in the Foretravel library if possible.

Pierce

Re: 1991 U300-- bought it!

Reply #126 – June 09, 2020, 07:10:30 pm

Here's some good Tips, Do's and Don't's from Donaldson filters.

I've been guilty of taking an air filter out and banging it on the ground to knock the dirt out and putting it back in... on my lawn mower but not my coach!

Jerry

https://www.youtube.com/watch?v=MJ2HViIGDeQ

Re: 1991 U300-- bought it!

Reply #127 – June 13, 2020, 11:56:24 pm

Generator is running with some hack!

It has been few days since I worked on the GV. I was reading a lot about the generator just to prepare myself to fix it. There is a great website [url=http://www.smokstak.com]Antique Engines Antique Tractors Steam Engines and Old Iron [/url]that has rich information about ONAN generator. The website allow me to read the content but I can't see any attachment or pictures unless administrator approve my registration. Spend quite some time on that site to read all information about the generator.

Overall, people are saying this generator is very reliable. It is old school mechanical generator. There is not many things can be broken. I like that. Less thing to break, less thing to worry.

The generator Model No. is ONAN 7.5DKDF J27798C. It use Kubota D950 engine supposed to be very reliable. I searched online, Attached is the operators manual I found online. Hope it can be helpful to others with similar model.

On Wed. I worked on the RV try to diagnose why the generator is not working. Based on what I read, if it is not starting, the first thing to check is the fuel line. First thing to check is the fuel pump. When I start the generator, there is no clicking sound from the fuel pump. It seem like the pump is not powered. I use multi-meter to measure am-page and voltage to the pump, it seems like the pump is not getting power. So I decide to take it off.

I sent few pictures to @stump. By looking at the picture, he think the pump might be able to be cleaned and reuse. That is a great suggestion. On my work bench vise, used a big channel pliers to unlock the end cap, there are oil filter inside the cap. NAPA sells this Facet filter and gasket kit, under their own part number, as a 610-1086, as seen, for under $10.00. I didn't buy new one. The existing one seems clean. Used some brake surface cleaner to get rid of some dust and put it back. Connect to my solar 12V battery and it worked! Another great suggestion from @stump!

During the process, I accidentally get the positive cable out of the pump. I am unable to get the middle cover out. Does anyone know how to get the cover in the circle out? The wire just barely stay in there. It is definitely not reliable.

According to the some online post, the Fuel pump is Facet 574A. It is very reliable. 30~50 year life is possible.

Now I know for sure the fuel pump is working. Next to check is to see if there is any other issue in the fuel line. @stump mentioned that there might be some air bubbles to block the fuel line. So Next thing to do is to bleed the air system. Luckily by reading the operator manual, there is build in bleeding valve near the fuel filter. Open the bleed valve. Run the fuel pump from external power. I see a lot of bubble come out from the bleed valve. What @stump recommend is definitely correct. I let the pump run for a few seconds until I see clear solid fuel come out from the bleeding valve. According the to document, there is no need to bleed to high pressure fuel line. It will bleed by itself.

By watching few videos of the same model generator, I noticed that the proper step is to preheat the glow plug, then hit the start button. Then the solenoid will retract, pull the level off the stop position. At this time, the generator will start

The adapter between the solenoid and the level is missing, so I have to manually pull the solenoid to simulate the step above. Push the level to open position and manually push the solenoid to retract position. The generator seems want to start, but not able to start. After a few tries, I think the fuel pump is not getting power. This is verified by opening the bleeding valve. There is no fuel come out.

So the problem now is the fuel pump is not getting power. All the logic surround the solenoid is causing the issue. I am thinking to by pass the solenoid, just run the fuel pump from external power. This should start the generator. So I connect the fuel pump to my car battery. I can clearly hear the fuel pump working. The solenoid is at the extended position. The level is at the open position

Preheat few second, then hit the start button. The generator fires right up! And it stays running for few minutes. I can't turn off the generator using the button since the solenoid is by passed. I have to manually turn off the lever to stop position.

That is great news. But is it generating power? to tested, I unplug the 110V power. Turn on the circuit breaker for the front and rear AC unit, Microwave. Turn the AC to max. Fire up the generator, and the AC is blowing cool air. So it is generating enough power for both AC and Microwave. It is working! It is very exciting. I texted the video to @stump .

Next just need to find out why the solenoid is not providing power to the fuel pump. I think there is some wire messed up. But at least the generator is working.

From what I read, to properly exercise generator, it needs to run under full load for 10 minutes or longer. I let the generator run for 15 minutes. Then shut off. Everything seems fine.

Next is to change the engine oil and filter and air filter for the generator. I couldn't find the fuel filter. So I didn't change that one. The parts I used are

Engine Oil
NAPA straight 40W.
The documents ask for straight 40W for 15C plus temperature. But the cap on the generator says straight 30W. I choose to use straight 40W since the 6v92 needs 40W too.

Engine Oil Filter
Cummins Onan 122-0833 Oil Filter from Amazon
Manual ask for 185-2123. But it is cross referenced to 122-0833

Engine Air filter
NAPA gold 6270
Manual ask for 185-2090

Changing oil is very straight forward. Open the valve at the bottom of the crank case, drain old oil. Change the filter. Refill new oil. I change engine oil on my car, so this is easy. However, I couldn't find anywhere in manual mentioning how much oil is needed. The only sentence related to oil change is to keep as close to full line on the dip stick as possible. So I added 4 Qts of the 40W engine oil and it is right at the full line. Please let me know if you know the exact amount of the engine oil needed?

The next thing I am going to check is the low voltage on the dashboard. I started up the engine, measured 12.54V at the alternator. It seems too low. Right at the alternator, it should be more than 14V. This is something to work on next.

Thanks for you reading!

Re: 1991 U300-- bought it!

Reply #128 – June 14, 2020, 12:22:44 am

Two things:

1. It is recommended practice on this Forum to start the generator with no loads on it. Allow engine to come up to speed and the voltage output to stabilize. Then turn on the loads (air conditioners, microwave, etc.). This is supposedly easier on the generator.

2. Alternator problem: can you take a better photo of the tag on top of the alternator, and also a photo of the rear end of the alternator where the wires are attached? Need to see the model number. Try to clean off the wiring posts before you take the photo. Once we see the photos, we will have a better idea how to advise.

It looks like you have a "duvac" alternator. If that is correct, the "sense" wire may not be connected correctly. You can search the term "duvac" on this Forum for some long-winded explanations of the term.

Re: 1991 U300-- bought it!

Reply #129 – June 14, 2020, 08:59:18 am

Hopefully the back of your alternator looks like the units in photos below. If true, then we know what we are working with!

See simplified diagram (Thanks to Neal Pillsbury) for DUVAC sense wire connection (Vr = Voltage reference).
Note: Sense wire can alternatively be connected to START battery post on isolator.

Re: 1991 U300-- bought it!

Reply #130 – June 14, 2020, 09:28:40 am

I sometimes wonder at myself that I find reading this kind of thing so very interesting. I will NEVER on this earth actually perform any of the steps that are so very well described by Jiaxinxi ... but for some reason, it is just so easy to read and follow and I am right there with him testing voltage.

Anyway .... waiting for the next installment!

Re: 1991 U300-- bought it!

Reply #131 – June 14, 2020, 11:24:53 am

I have the exact generator in my coach, here is a little problem I found with mine. Ive found running the gen. then shutting down for the night. Get up the next morning getting ready to go. Checking coolant and oil in both engines. I pull the dipstick on the gen and theres no oil on it! Im thinking wow what a little oil burner. So I add 2 qts of oil to it. The next week I get ready to take off, the gen is 2 qts over full. What I learned, the seal on the dipstick wont allow any air out over night. When you pull it, it looks like its out of oil. So now when I check my gen. oil. I pull the stick, wait a few seconds then check the oil. Its weird even saying the dipstick is way to good at doing its job.

Re: 1991 U300-- bought it!

Reply #132 – June 14, 2020, 04:10:53 pm

If your generator supply hose is OEM, you may be sucking some air into the system. With a magnifying glass, bend the hose back on itself and look for tiny cracks. Hose is easy to replace and only takes 15 minutes or so if you have a crow's foot for the fitting on the tank and a long rod to attach the new hose on it. The original hose snakes it's way to the tank fitting so attaching it to the old hose is not recommended. Don't slide the generator out as it's best done with the generator in operating position. Leave enough hose to allow for the generator in the out position. Ours is a 1993 so two years newer than yours and this was our problem.

When the generator stops for seemingly no reason, it's usually the hose. With the fuel tank is low, but above the generator pickup, the fuel has to be lifted further (no siphon if hose has a leak) if the hose is leaking, air may be introduced. If you have a good hose, the level of the tank won't make any difference if above the generator pickup in the tank. If you run the pump with a jumper and you see bubbles in the pump discharge, air is getting in, at the tank fitting, hose leak or fitting at the electric pump. Should be nothing but diesel.

Round style Facet electric pump is excellent. They were first made as Bendix and lots of clones are available for $20-$25 on ebay. Aircraft supply stores are probably the least expensive if ever need one. As I remember, the bottom hex is 5/8" to remove to get access to the filter. The nylon filter is then easy to remove. We have to do that on annual aircraft inspections as the Facet is usually the aux fuel pump on thousands of planes.

Pierce

Re: 1991 U300-- bought it!

Reply #133 – June 14, 2020, 04:28:44 pm

The fuel filter is that black spin-on right under the bleed valve you pointed out. Attached is something I made years ago showing various parts of the generator. You can see the linkage for the Start/Stop solenoid. It looks like the ball joint link broke on yours. I would take it apart and see if a local parts place might be able find something that will work. Otherwise McMaster-Carr probably has something genereric that will work. The thread on mine appears to be 1/4-28.
McMaster-Carr
Search for Ball Joint Link

In regards to the fuel pump connection it looks like that piece is non-repairable; might have to buy a new pump.

Re: 1991 U300-- bought it!

Reply #134 – June 15, 2020, 01:06:07 am

Can you see if this is a DUVAC alternator?

Model. No: 25-15

Re: 1991 U300-- bought it!

Reply #135 – June 15, 2020, 01:21:34 am

It looks like the feed wire post has been overheated at least from the picture.

Re: 1991 U300-- bought it!

Reply #136 – June 15, 2020, 01:24:04 am

I seriously recommend having it rebuilt. Too important not to renew it IMO

Re: 1991 U300-- bought it!

Reply #137 – June 15, 2020, 01:32:20 am

At least clean the posts and conections. Be careful removing the nuts.

Re: 1991 U300-- bought it!

Reply #138 – June 15, 2020, 02:14:36 am

Foretravel used the adjustable voltage alternators so you could turn it to match the temps and battery types.

Re: 1991 U300-- bought it!

Reply #139 – June 15, 2020, 08:25:32 am

Quote from: jiaxinxi – June 15, 2020, 01:06:07 am

Can you see if this is a DUVAC alternator?

Model 25-15 is a common OEM unit on older coaches. This is the same cable connection setup as the ones shown in my Reply #129, so pretty confident it is a DUVAC unit.

As mentioned above, remove the cables and clean up the connections. Apply some penetrating oil to the studs and let it soak in. Try to use a backup wrench at the base of the studs when you remove the fixing nuts. You DO NOT want the studs to turn.

To avoid sparks, disconnect the big positive battery cable at the battery end before removing it from the alternator stud.

The small gauge wire on the small post (nearest the big POS post) is the SENSE wire. While you have it disconnected from the alternator, try to determine where the other end is attached. As shown in the diagram in Reply #129, it should be connected to either the POS battery post on one of the start batteries, OR to the START battery post on the isolator. If you can find the other end, test the continuity of the wire with a multimeter. If there is no continuity (open circuit) see if there is a fuse holder somewhere in the wire. Might just be a blown fuse.

With SENSE wire correctly connected the SENSE terminal on the alternator, when checked with a multimeter, should always read same voltage as START batteries.

Once everything is cleaned up and reconnected, see what kind of output you are getting from the alternator. With engine at idle, you should see around 14 volts at the POS alternator output post.

Don't mess with the adjustment screw on the top of the voltage regulator until you have done the other steps above. The adjustment screw is very sensitive! A small movement of the screw will make a big change in voltage output.

Re: 1991 U300-- bought it!

Reply #140 – June 15, 2020, 01:59:54 pm

My sense wire came from the fuel run solonoid . About 12 in from the alt.

Re: 1991 U300-- bought it!

Reply #141 – June 15, 2020, 02:23:53 pm

Quote from: Protech Racing – June 15, 2020, 01:59:54 pm

My sense wire came from the fuel run solonoid . About 12 in from the alt.

I would probably choose a location less "distant" from the chassis battery-- you really want it to accurately telegraph voltage. If it has run through the ignition circuit up front and back to the engine, it may certainly be adequate to hold open the run solenoid, but may be several tenths of a volt lower than actual battery voltage. This can lead to high voltage/overcharging of the batteries. And, even if perfect when new, a little resistance in all those yards of wire and many connections can give lower than actual readings to the alternator.

I like chassis battery lug of the battery isolator or other source directly connected to the chassis battery by large-gauge wires.

Re: 1991 U300-- bought it!

Reply #142 – June 15, 2020, 03:24:59 pm

Mine was Oe that way. I'm happy with the charge rate and voltage. 13.7 ish.
The duvac charges in cycles. Drops to 12.4 , engages until 13.7 . Sorta like the air system.
I also have a 100 amp delco running the house side. The boost combines them of course as does the OE charge controller.

Re: 1991 U300-- bought it!

Reply #143 – June 15, 2020, 08:51:46 pm

The powerline alternator was a knock off of a Leece Neville. It was a little cheaper. Foretravel used them for a while. I would have it rebuilt and it is a DUVAC.

Re: 1991 U300-- bought it!

Reply #144 – June 15, 2020, 10:03:32 pm

Hehr Powerline is out of Ft Worth, TX. You can check with them for dealers they trust to rebuild their alternators.

There is one in Pearland where I had one rebuilt a couple of years ago: Alternators and Starters Pearland Alternator Co., Inc. Alternator, alternator...

But, please completely troubleshoot your charging system before doing anything. A bad battery isolator and bad alternator can have very similar symptoms.

Re: 1991 U300-- bought it!

Reply #145 – June 22, 2020, 05:17:09 pm

It is a little bit slow for me to work on the coach since it is in storage now. But I am still working on it.

Follow your guys suggestion and @stump guidance, I did some clean up on the all battery terminals.
Alternator Positive/Negative, Isolator all three posts. Starter solenoid, basically everywhere the battery cable is connected, I used metal wire brush to clean the rust and dirty away. Use some circuit board cleaner to remove grease, then put it back.

After all the cleaning, the voltage is still low on the front voltmeter. So most likely the alternator is not functioning well.

I called the Hehr powerline manufacture, they said they can certainly rebuild this model 25-15. But it is at least $500. They can sell me a new one Model No. 25-26 for $900, plus tax and shipping, total about $1000. That is a lot of money.

Called the company recommended by @wolfe10 , they said they are able to rebuilt it, but I am not very sure since this one is so old.

One of the HEHR powerline technician told me a trick to test if the alternator is good and just the regulator is bad.
There is a small hole between the two small post. Using a paper clip in stick into the hole and connect with the sense wire, this way, the voltage regulator will be by passed. If the voltage increase with engine RPM increase, then the alternator is good, regulator is bad.

I haven't tried yet. but thought this is good to share to you guys.

When I clean up the connections, I measured the voltage on my battery isolator, I noticed that the three post of the isolator will always hot regardless of the engine running or not. When engine is off, All three post on the isolator show the same voltage. I don't think that is correct based on my understanding on how it works. I think when engine is off, the post connect to the alternator shouldn't have any voltage.

Do I have a bad battery isolator too?

Re: 1991 U300-- bought it!

Reply #146 – June 22, 2020, 07:12:31 pm

Quote from: jiaxinxi – June 22, 2020, 05:17:09 pm

When I clean up the connections, I measured the voltage on my battery isolator, I noticed that the three post of the isolator will always hot regardless of the engine running or not. When engine is off, All three post on the isolator show the same voltage. I don't think that is correct based on my understanding on how it works. I think when engine is off, the post connect to the alternator shouldn't have any voltage.

Do I have a bad battery isolator too?

Six years ago, not long after we purchased our coach, I encountered this exact same situation with our OEM diode isolator.

I posed the same question to the Forum, and we ended up having a lively discussion about this subject. See link below:

Bad Isolator?

Note: The thread linked above does not include my final decision concerning the health of my OEM isolator. In Reply #22, Peter Fleming (a very sharp Forum member) suggested several tests that required DC current measurement. I purchased the meter he recommended, and performed the tests. I came to the conclusion that my OEM isolator was working fine. I ended up leaving it in place, and it performed exactly as designed for the next 4 years. Then, two years ago, I removed the (still functioning) OEM isolator during a complete rebuild/upgrade of my isolator panel.

But that's another story:

'93 U280 Isolator Panel Upgrade

Re: 1991 U300-- bought it!

Reply #147 – June 22, 2020, 08:01:12 pm

Just found this topic. Really enjoying it. I have to admire and respect the work your putting into your coach. I have no suggestions from what I've read except that when cleaning the electrical connections, I would be sure to use die electric grease to help prevent future corrosion. Keep the posts coming.

Larry

Re: 1991 U300-- bought it!

Reply #148 – June 22, 2020, 09:12:54 pm

Quote from: jiaxinxi – June 22, 2020, 05:17:09 pm

When I clean up the connections, I measured the voltage on my battery isolator, I noticed that the three post of the isolator will always hot regardless of the engine running or not. When engine is off, All three post on the isolator show the same voltage. I don't think that is correct based on my understanding on how it works. I think when engine is off, the post connect to the alternator shouldn't have any voltage.

Do I have a bad battery isolator too?

The output terminal on an alternator is always connected to the battery. Unlike a generator that always has some residual magnetism and because of its design can boot strap that magnetism into full output, an alternator always requires an external source of voltage to start.

Re: 1991 U300-- bought it!

Reply #149 – June 22, 2020, 10:30:05 pm

Quote from: Old Toolmaker – June 22, 2020, 09:12:54 pm

1. The output terminal on an alternator is always connected to the battery.

2. ...an alternator always requires an external source of voltage to start.

1. In the case of the charging system being discussed here (dual batteries, diode isolator + duvac alternator) the output terminal is not connected to the battery. It is connected to the center post on the diode isolator.

2. This is correct. Since, in this case, the output terminal is not connected to the battery, the alternator must receive the voltage by some other means. Hence the requirement for a voltage SENSE wire which is connected (directly or indirectly) to the start battery positive terminal.

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