The "Problems" continue

Blacksheep · January 08, 2009, 04:33:01 PM

The charging problem I HAD is NOW gone! That's a plus and to boot, the batteries don't continually drain while sitting over night. In fact, they have stay pretty charged since replacing the R3 Relay. I have read everyone's opinion on what the charge rate should be set at and re-read the charts everyone supplied and came to the conclusion that I needed to adjust the regulator to bump the rate up just a tad! Well, to do this the coach needed to be started so today I had time and went out to start the bus. It cranked a little longer than normal but started. It just didn't sound quite right so I shut it off. I raised the engine door and looked around to make sure a squirrel or SOMETHING hasn't done damage. None found so, I restarted and the same result but this time I tried to accelerate and there was NO throttle response. Looking at the tach, it showed only 300 rpm and stepping on the pedal made no difference. Now I'm stumped. I tried the high idle and nothing. OK, now I'm thinking electronic since that is what started all the trouble. I start checking relays, breakers, wires, and anything else I could think of. I got the book out and read up on fuel delivery. Didn't tell me much more than what I already knew but I DID learn that the throttle won't work IF the ddec test switch is in the ON position, which it wasn't so back to the drawing board. I called my friend Brian Joy who is the regional service guy from Prevost. I call him a friend since he has heard my voice so much he knows me by name although we have never met. I explain my woes and he says that there is nothing electronic tied to the coach that relates to the fuel delivery and says to start with the filters. If I still have a problem it could be the fuel pump OR since I have had the voltage problem it COULD be the ECM going bad. Uhh, not what I wanted to hear but none the less, I had to start somewhere so changing the filters was the thing to do. After siphoning (yuck) fresh fuel from the generator tank into a can to fill the new filters that I installed, my friend Niles from Tampa who also owns a Prevost H model gave me a surprise visit along with a VERY LARGE Pizza. The Pizza had to wait as I just had to see if the filters did the trick. It started, It idled at the normal idle and it accelerated by the pedal. Next was to see if the high idle worked and it did too! All is now good but don't you find it peculiar that this happened in my driveway with absolutely no warning? I do but for now, it's charging like it should and running like it should, for NOW!
I DID learn a lesson from all of this. Just because you have one problem fixed and another pops up soon after, don't think they are always related! In this case they weren't but I'm sure they could have been! One way to keep the mind working for sure!

Ace... ready to roll!!!

Len Silva · January 08, 2009, 04:39:41 PM

I don't know what it was but obviously you did SOMETHING to piss off the gremlins.

Blacksheep · January 08, 2009, 05:00:31 PM

Yes tell me about it! Now get this. I just came in from outside and I dumped the fuel from the filters into a glass jar and the scary thing is, it's pretty darn clean! No trash, no water, nada!

Does anyone know a good way to cut the filters open besides using the filter cutting tool? I'm just curious as to why and IF this actually fixed my problem?

Ace

Utahclaimjumper · January 08, 2009, 05:12:14 PM

I use a large tubing cutter just like the small ones you would use on copper tubing, Ive had it for years and even then was a pricey $90.00, but it works great by holding the closed end in a vice and cutting off the end at the threaded end. The whole filter falls out of the tube and can be seperated and looked at in the sun, its amazing what youll find>>>Dan

NJT 5573 · January 08, 2009, 06:23:53 PM

Ace, the fuel we get now days is pretty good stuff. A few years ago the filters would plug about every 8 months if you operate every day. Now they go over a year and what the catch is very small in size. We used to pour a mix of stuff that you could see out when we looked at the old fuel, but now its not unusual to have a plugged filter and pour out clean looking fuel.

I still use a hack saw to cut mine, I know what the metal from a saw looks like and I just discard that when I look at the paper and most of it falls outside anyway.

I have heard talk of biocide use especially with a biofuel mix but I don't know that anything is growing in your tanks. Last winter I used a biocide in my tanks and was concerned that if it killed something I would plug the filters anyway. No plugged filters so I guess nothing was growing in my tanks. My local fuel dealer told me that they are putting the biocode in their bulk tanks anyway.

I only buy non biodiesel and I only fuel at high volume truck stops and have not had a problem yet. Hope that filter was just used up and not plugged by recent contamination.

Hopefully the filter was full to the top and you don't have a sucking air situation.

I never go anywhere without spare filters just in case.

Blacksheep · January 08, 2009, 06:38:24 PM

Well to update, I went out and cut open the smaller filter and found nothing weird inside other than black or very dark colored wet paper. I couldn't see any light thru it as I held it up to a bright light so not sure what this tells me if anything! I want to believe that the filters were just clogged to the point that they wouldn't pass fuel enough to run but that still doesn't explain why I had no peddal response!

Does anyone know what the fuel pressure spec is supposed to be on a 8v92? If I were to install a fuel pressure gauge, first is this a good idea and would it mount directly to the fuel filter housing? I see a fitting on top that is plugged. Would this be a good place? I also carry extra filters on my trips! I guess you just never know!

Ace

white-eagle · January 08, 2009, 07:26:18 PM

look for a gremlin named susan. she's probably lhao about paybacks for bucket heads

Blacksheep · January 08, 2009, 07:39:32 PM

LMAO but that reminds me Tom, bobofthenorth sent me a pm inviting us to meet him at Wally World. Seems his wife needs a new "bucket" and he needs help finding the right size! Are you still in Florida or are you in Texas now? Did you go by the service place I told you about? If so, how was it?

Ace

white-eagle · January 08, 2009, 07:44:03 PM

did, good, more to follow.
we're in polk city overnight, then on to Bushnell and Texas.
fran wants a couple miles on her bus first before posting results.

Greg Roberts · January 08, 2009, 08:49:17 PM

Ace,
I recall a fellow told me that the fuel pressure on the 8V92 and the 6V92 are the same. I recently learned that the fuel pressure on my 6V92 is supposed to be 15-20 PSI at idle and somewhere between 50 and 70 PSI at the high RPM. I placed a pressure gauge on the top of my secondary filter where the plug is located that you mention and verified my pressure at various rpm. There is a very distinct pressure profile on a unit with a good pump and no air mixed with the fuel. On my unit I had both a weak pump and a air coming into the line from the fuel tank. My engine would idle low and high just fine but would not run up to 2100 rpm. The pressure at idle was 15-20 and it would rise up some when the throttle was pressed but would fall back as rpm increased. This fall back was from the air in the fuel. the pressure should rise as rpm rises and not fall back except when under heavy load. The gauge installed at this location is invaluable and I would suggest everyone do a run up now and then as a preventive test to verify good pump and a tight fuel system. Of course you will want to make sure you have fresh filters when you do this check. Hope this helps. - Greg

Quote from: Blacksheep on January 08, 2009, 06:38:24 PM
Well to update, I went out and cut open the smaller filter and found nothing weird inside other than black or very dark colored wet paper. I couldn't see any light thru it as I held it up to a bright light so not sure what this tells me if anything! I want to believe that the filters were just clogged to the point that they wouldn't pass fuel enough to run but that still doesn't explain why I had no peddal response!

Does anyone know what the fuel pressure spec is supposed to be on a 8v92? If I were to install a fuel pressure gauge, first is this a good idea and would it mount directly to the fuel filter housing? I see a fitting on top that is plugged. Would this be a good place? I also carry extra filters on my trips! I guess you just never know!

Ace

Blacksheep · January 08, 2009, 08:52:01 PM

Greg thanks for the info. What type gauge did you use?

Ace

Sojourner · January 08, 2009, 08:57:14 PM

My suggestion is not necessary a must have but because of the unknown fuel condition from algae or bad fuel or collapse hoses...the following installed gauges will guarantee to pin point the problem from the fuel pickup, hoses, filters, broken injector's line and fuel pump.

See if you have restricted filter or not or partial...even collapse hose.
1)   Install a tee between primary filter to gear pump.
2)   Install a tee between gear pump to secondary filter.
3)   Install a tee between secondary to cylinder head (fuel manifold to injectors).
4)   Install a mechanical 0-30 HG vacuum gauge in # 1 tee.
5)   Install 2 electric 100 psi oil/fuel pressure gauge. One for each...# 2 & # 3 tee.

While in driving in accelerating mode and hill climbing mode...you must watch the gauge in the order of sequence 1- 2 - 3:
1)   For higher vacuum of more than 5% than baseline. Primary or tank inlet or collapse hose is restricted.
2)   For # 2...higher psi of more than 10% at warm temperature and # 3 is lower psi than # 2. Secondary filter or collapse hose is restricted.
3)   For # 2 & # 3 lower then spec psi is one of two things...broken injector's line or weak fuel pump.

Caution: The % figure is only my suggestion...it can be higher due to very cold fuel ...you need to do the road test and reports your finding.

About the source for gauge...Marine supply and auto parts store.

FWIW

Sojourn for Christ, Gerald

BTW...I start this 3 hours ago but didn't finish till now and learn of Robert's good information about air in fuel system.

NJT 5573 · January 08, 2009, 10:27:23 PM

Ace,

There is a DDEC sensor mounted at the filters. No flow/fuel, no throttle. It has given me fits when trying to prime the DDEC system until I unhooked it, then I was able to bring the RPM up enough to burp the air out of it. Probably not smart, I think its probably there to protect those spendy electronic injectors!

JackConrad · January 09, 2009, 05:40:48 AM

Ace,
We installed 2 fuel pressure gauges on our 8V71. We have a mechanical gauge in the engine compartment and an electrical fuel pressure gauge in the dash. Both are connected to the output side of the secondary filter(after the fuel pump). As was mentioned we run about 15-20 at idle and about 65 at higher RPM. Although we have not had any fuel issues since the delaminated supply line to the primary filter, the gauges are a great diagnostic tool Wish I had the gauges when we had the fuel line problem, it would have made trouble shooting much easier.
The Wet Black sounds like algae. Jack

Len Silva · January 09, 2009, 05:48:05 AM

Just out of curiosity, what fuel pressure would you expect at cranking speed? Might help diagnose a no start condition.