• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

6.5TD motorhome starting problem

Will L.: I plugged the engine heater in for 11 hours. Checked temp on both sides of engine at one glow plug. Passenger side at 95 degrees. Driver's side at 120 degrees.
Turned key to on....glow plug stayed on for 5 seconds (probably due to heat in engine). Usually stays on for 10 seconds. Turned key to start and it took maybe 3 or 4 seconds...just like my car.
Please remember I installed a new glow plug controller and 60G glow plugs.
Let me know what to try next? (Maybe glow plug wires are going south?)
Thanks again for all your help!
 
Has anybody had time to read the above test sent to Will L to answer his questions. But I haven't heard back from Will L. and would like to know if anybody has read the results and have something I can try next?
Could it just be newer wires to the 60G glow plugs? How many of you have changed your glow plug wires when you changed all eight glow plugs?
 
With no air coming into the fuel system- i doubt the problem is on that end although I don’t recall you answering what volume of fuel is being output. Basically how long to supply 1 pint or 1 quart from the fuel drain line being pumped by the lift pump. When you do this test pump it into a clear clean container like a mason jar. Put a lid on it and let it sit undisturbed so that anything that might settle out has the chance to over a few hours or even overnight. If everything is clean just use a funnel and pour back into the tank.
You replied the filter was changed “regularly” or something like that. But understand 1 tablespoon of water will put the stock filter at its limit and water can get through with the forced fuel as well as with a weak lift pump which we all believe you have - it might severely restrict the flow of fuel getting through.

Once the engine is started the ip has aan internal transfer pump that is designed for boosting internal pressure and internal flow regulation. It has a side effect of sucking fuel from the fuel filter when fuel pressure is low. Yours has been doing this at your pressure and it wears out the ip faster than normal. When it does it under 1 psi it very quickly wears the ip. I can’t emphasize enough how important this is.

Leroy’s filter tap bolt is nice but only tells 1/2 the story. If you can not get a metal T fitting installed right now, at least use an inline T and as short as possible new rubber hose from that T to the ip fitting. It is 5/16 hose from the factory.

There are things I recommend for long term use but it becomes questionable on a motorhime that doesn’t get a lot of miles. Solving the issue at hand is best done without firing the parts cannon if possible. If you keep the factory ffm doing the ftb mod so there is 3/8 feeding tank to ip instead of tank to ffm then the reduced 5/16 from ffm to ip. Your lift pump is already known to be too weak but replacing with another mediocre pump might be the option for economical reasons. But 5 psi should be ample to start ok.

The original fuel line is most likely not rated for the modern fuel and deteriorating from the inside out. We don’t know because the rv company can put in whatever they want. So using BOTH volume readings and pressure AT THE IP becomes critical at this point.
Long term whats best? All new sae30r9 or greater fuel line.
Fass LP with their filtering system and fuel heater, then eliminating the factory unit as it is sub par for the modern fuel we have since they add ethanol/ methanol to our fuel. And the metal tap at the ip with the FTB fitting there so it is 3/8 at the smallest point. But I don’t want to send you that route as it will be about a grand and may not solve the hard start- it will definitely help the fuel system long term.

With the block heater eliminating the long crank time that says it’s a heat issue so testing the power to each individual glow plug wire is in order. With no power you can ohm them out as well. Pay close attention to how well they clip onto the plug- loose connection there can be its own issue. The 120/95 difference is expected, there is only one block heater and you can guess easily which side it’s on. Adding a second one in the other side is something folks in rough areas do, among additional heating pads to oil & transmission pans.

It might be the glows are working properly but the additional heat is enough to make it much better.
Something I don’t remember asked is what cranking speed do you have?

Where you have the fuel pressure tapped is pre filter. While that is a good place to know that the lift pump is working it doesn’t tell us the pressure actually getting to the ip. With it being low and especially because of the bl ed off of pressure and the fact that cycling the key a few times helped- we really need to know the pressure at the ip inlet. My recommendation is a metal T fitting at the ip so there is no rubber hose after the tap. I have seen degraded hose be the problem so many times… several people here and more from outside this forum have replaced good working ip and had the same issue only to find the hose was the problem all along.

You said the injectors were recently rebuilt. Can you say by who and at what pop pressure? Were they balanced within 25psi of each other or just to basic spec?
 
Oh, and don’t wait just for my latest responses- first there are plenty of folks here that are hitting key issues and can easily solve the 6.5 problems without my input.
My methods I would argue are encompassing and have awesome long term results but only by justification of getting a couple hundred thousand miles from a 6.5. My methods certainly are not the low cost ones.
 
Will L. said:
Gen-
He only has it when cold starting and there is air coming out of the ip inlet the return line so air is not the issue.
Click to expand...
Replace seals at fuel sender unit. Better yet, replace sender and the fuel lines from sender to Lift Pump. You suck in air back there and it creates air in the system and starting problems. Been there twice on these vehicles in the last couple years.
 
With heat confirming the long crank time getting better, after testing each wire to the GP's and confirming 12+ when not connected, then it could be that you need more GP run time. the factory PCM was programmed at GM for the 11g GP's which get hotter quicker, but they burn out fast too. a double edge sword. try rigging up something to bypass the GP controller weather you use a screwdriver shorting across the controller contacts or wire in a second solenoid and a push button in the dash to do the same.

key on and let the PCM do it's thing with the wait to start, then manually override turning the GP's on for another 8 to 10 seconds, then crank and see what happens without the block heater.
 
When I installed the 60g GP's I quickly found out the PCM wasn't providing enough run time for them to get hot enough. 60g's are slow to warm but are regulated so they don't overheat and expand blowing off the tip and destroying the engine.

Once I figured this out, I wired in a time delay relay into the yellow wire going into the GP controller. this overided the PCM and allowed me to set how long I wanted to GP's to stay on for every time I turned on the key.

This is the delay relay I used. https://www.amazon.com/dp/B071XNY72Q

it requires iirc an ignition switched power source, ground, and the output would go to the yellow wire on the GP controller for 12v+. If your interested in this let me know and I can help you wire it up so long as the 5 pin connector on your GP controller only uses three wires (95+) not the older style controller.

1743775676656.png
 
I installed the new wire harness before installing the new long block.
I had never experienced extended cranking times or issues with GP cycles but that new harness shortened the already short crank time.
Now with this new ECM, a longer GP cycle has been programmed into it and that has shortened the crank time even more, that and the new PM starter.
 
dbrannon79 said:
With heat confirming the long crank time getting better, after testing each wire to the GP's and confirming 12+ when not connected, then it could be that you need more GP run time. the factory PCM was programmed at GM for the 11g GP's which get hotter quicker, but they burn out fast too. a double edge sword. try rigging up something to bypass the GP controller weather you use a screwdriver shorting across the controller contacts or wire in a second solenoid and a push button in the dash to do the same.

key on and let the PCM do it's thing with the wait to start, then manually override turning the GP's on for another 8 to 10 seconds, then crank and see what happens without the block heater.
Click to expand...
If it’s air getting in the fuel system overnight. Heat has nothing to do with the confirmation of anything. It is all about the purging of air in the fuel system, which then leaks down again after sitting overnight.

I don’t know what the OP has addressed, but he needs to make sure all the injector returns are new and not leaking. He needs to trace back from the IP to the LP to the tank for any leaks or sources of air intrusion.
 
ak diesel driver said:
5 seconds should indicate that it's taking that long to refill everything. If it only lost pressure it should build pressure immediately
Click to expand...
I agree.

Except his lift pump is only putting out 5 psi, which may indicate the lift pump is not up to snuff, in which case it may take longer to get up to pressure.

Back to things already discussed.
 
it is absolutely normal to gain a small air bubble when the engine shuts off. If you read the pump manuals it is explains this and is why the hose is sent into an upside down U shape, to trap the air rather than sending a large amount down the return line when the engine starts which could cause an issue.

If he was loosing enough fuel to drop all pressure then draw air into the line, he would have 0 psi then build to his pressure. And when cranking it would expel the air easily visible in the clear line. If that was happening I would have told him he immediately. But because he is able to build over 3 psi before cranking AND NO AIR BUBBLES TRAVELING in the return line- that is not the hard start cause.

It very well could be he is wiping out the ip transfer pump on the freeway or during hard acceleration but watching his pressure gauge once tapped at the ip inlet is the only way to know. For now- focused on the hard start issue.

When he did the 120v heater plugged in, that solved the majority if not the entirety of the hard start. Remember he is probably running low capable cables, and an old POS stocker starter. Hence why I asked cranking rpm. If it is cranking 200-250 rpm and everything else is in average condition, then temps in the 40’s, 5 seconds is a perfectly normal crank time on 60Gs.

Magic wand and spending all his money- absolutely new fass unit with 1/2” line feeding until the FTB 3/8 fitting at the ip. Then well sized cables to a powermaster 9052 to spin that engine like a top and easily force a faster start. But upgrading the whole rig is maybe not what he is after. So I am trying to focus on changes that have biggest impact for the dollar and will last longest.

Take the pressure readings at the ip will tell a lot. He could be getting 5 at the filter and 2 at the ip. Starts cranking and it dips negative (vacuum) for a moment. But this is speculation.
Until we know there is bubbles traveling in the return line, the LP is keeping up with starting requirements. So…

@beezer1999
How many miles you plan to run this, what money you are willing to put in on upgrades/repairs, if you prefer more expensive on & done verses lower cost but repeating same parts changes later… this is info we need from you to make recommendations where to go from here on replacing the LP with similar to what you have/ mild upgrade/ maximum upgrade is variable and somewhat preference.


Doing starter, cables, etc just for better starting- how much money is worth that now verses waiting until the current starter dies. With the miles you have the current one might last another 70,000 miles or die next week because of working harder to start could have been hard on it. Assuming you have the Delco mini high torque starter as it was most popular at the time your rv was built, however some applications were still getting the huge direct drive VERY SLOW spinning prestolite or Delco starters. If this is the case the powermaster will spin the engine at almost twice the speed which makes a MASSIVE difference how quick the engine starts.
What size battery cables you have and what condition they are in is also very important here. I don’t suspect either is heavily worn out as 99% of people have the instinct there is a “starter problem” and ask directly about it or say it seems to crank too slow.

So please- check the rpm it cranks at. Let us know that and about the injectors. Then what your targets are for cost vs improvements and usage.

Because once it’s up and running happily, 90% of us are gonna wanna talk about replacing that miniature turbo that they come with for one that WILL pay for itself in mpg savings while giving more power and extending engine life. But that only if you’re gonna put some descent miles on it. If you are under 5,000 miles a year… might not be worth it for mpg.

Monitoring ect is my biggest freak out on these. Factory gauges usually are horribly inaccurate and never letting it get to 220 is major. Checking on your harmonic balancer is critical at this point as is the oil cooler hoses. These are instant engine killers and all your stuff is old enough to fail by age not miles.
So this is why I don’t wanna spend your whole budget on 3 second starts rather than 6 second starts.
If you’re after great improvements and dropping $5,000 doesn’t bother you at all- then let us know and you can make major improvements with that.

Happy Saturday folks!
 
You must log in or register to reply here.
Back
Top