Diesel RV Club, an FMCA Chapter

Ask Dave => Hey Dave, I've Got a Problem => Topic started by: Vorlon on January 28, 2018, 11:07:03 AM

Title: Slow Crank
Post by: Vorlon on January 28, 2018, 11:07:03 AM

This is an epic saga!

I have a 2003 Gulfstream Friendship Quattro. The unit has a 3126 7.2l diesel engine. It has 80,000 miles on the clock. I bought the unit in October 2016 and hired a driver to deliver it to my home about 2,000 miles away. It was driven here and according to him it performed perfectly.

It was winterized and parked in my driveway for the winter. When I came to start it in the spring of 2017, it cranked very slowly and would not start. I figured oxidised or rusted battery leads, so I cleaned them all. Still slow crank! I took the batteries out and tested each on a car I have. Both performed perfectly. I then figured perhaps the solenoid. I finally found the exact model (new) and purchased it. After installation still slow crank and no start. I then figured that the starter motor was flaky so finally found the identical starter motor (new) purchased and installed it. Still slow crank 

Finally I gave in and purchased two new batteries (1000CCA) group 31. Made no difference, the crank is too slow to start the unit.

So now I have absolutely no idea what else to look at. Now that we seem to be getting the odd day above freezing, I wanted to sort this out hopefully before my better half gets on my back about a wasted purchase that we have never been able to use! Phew! Any help would be greatly appreciated .



Title: Re: Slow Crank
Post by: ziggyh on January 28, 2018, 05:52:17 PM
What voltage is at the starter when trying to crank compared to voltage measured at the batteries while cranking.  You should be with in a 1volt or less between the two.  A higher differace indicates an excessive voltage drop over the battery cables.  If that is the case you are looking for a bad cable connection or cable on the positive or ground side. You could also try using a set of booster cables to supplement the ground and positive side connections to the battery if you are unsure of performing a voltage drop over the positive and ground side connections.

Is the engine oil fairly clean and of the proper viscosity for the temperature you are in.

I have also seen a bad or seized accessory like an alternator with a seized bearing create a problem, remove the accessory drive belt and see if there is a difference.

Hope that helps.
Title: Re: Slow Crank
Post by: WILDEBILL308 on January 29, 2018, 08:30:06 AM
What is the temperature when you are trying to start? If  it is cold did you run the engine heater?
Title: Re: Slow Crank
Post by: ziggyh on January 29, 2018, 06:25:14 PM
Bill, I defiantly agree, Heat is a given, I don't  even try and start my cat when the temperature gets close to freezing without preheat.  Yes I know someone will say my deisel will start with out heat at -20 and some do, but it also matters on the year, engine design, and type of fuel system design and starting aids.
Title: Re: Slow Crank
Post by: Vorlon on January 30, 2018, 05:25:57 AM
Hi Ziggy and Bill,

Thank you so much for your replies. To fill in a little more information ... The RV is a 2003 Gulfstream Friendship Quattro. I purchased the unit late in 2016, A hired driver drove it from Alberta through freezing weather to Ontario about 2,000 miles and he reported that it performed excellently. It was winterised and parked for the winter. In the spring, I tried to start it (temperature well above 0) and it would not start. As the months passed during 2017 I pursued all the normal things ... cleaned all visible starter motor and battery terminals (there is a ton of protective popcorn covering around all leads and the chassis). I then replaced the solenoid and then the starter motor. Problem persists. Ziggy, i noticed on the battery guage on the dashboard that as I crank after about 4 seconds the voltage displayed drops from about 14 volts to 9 or 10 volts. I am assuming the feed for the battery guage comes directly from the starter motor and not the battery. I have connected the starter motor ground lead directly to the battery but there is no room to connect the positive clamp to the starter motor and then attach to the positive battery terminal. I have no idea how one would 'heat' the engine. Is there a built in procedure?  We have been dumped on again with the white stuff (our weekend of +5C was obviously mother nature's attempt to tease us and we are back to -9C so I am unable to check oil or anything else right now. Any further ideas would be appreciated.

Thanks again for the help



Title: Re: Slow Crank
Post by: Hey Dave on January 30, 2018, 09:02:45 AM
Slow crank sounds like loose ground in between batteries or batteries that check out good but only have a surface charge. Did you load test batteries?
Other possibilites:
- Grounds on starter need three (ground lub back on starter to batteries, same ground lug wire to side of block on top, back of head to ground post on batteries).
- Ground cables not heay enough to carry current draw.
- Last is this a Caterpillar starter and replacement Caterpillar starter or aftermarket starter.

Sorry for the delay in responding.

Dave Atherton, Retired Caterpillar Mechanic
Title: Re: Slow Crank
Post by: Vorlon on January 30, 2018, 09:18:29 AM
Hi Dave,

Thanks for the response. I replaced the batteries (supposedly new, I sure hope so). I actually tested the old ones on an old 6.5l Bentley(1968) which started instantly so I think bats are OK.

There are numerous connectors onto the starter both negative and positive. I did not see or clean up any connector from ground to the block! so amybe??? I did use a heavy duty cable to supplement starter ground to battery negative.

This is an original new Cat starter motor and Solenoid.

Thanks again,


Title: Re: Slow Crank
Post by: ziggyh on January 31, 2018, 05:17:35 AM
Dave, I would suspect that you have a block heater and there sometimes is a switch to turn on somewhere in the coach. Mine is at the base of my bed and will get power when the generator is running or on shore power.  I have seen some coaches that have the block heater cord tied to a harness in one of its rear compartments. Coaches that have aqua hot systems usually have a preheat function as part of that system.

I'm not sure where your dash gauge gets it reading from but I would suspects it comes from the battery side.  I'm not a fan of using the dash gauges and would prefer to use a voltmeter.
I would measure what voltage is at the starter when cranking right at the ground stud and the positive post. It should read very close to the same as what you measure right at the battery posts when cranking.  If there is a big difference like 1.5 and more that indicates that there is a loss between battery and starter connecting points.  That could be from a bad cable or connection.

The voltage when cranking at the battery will drop to about 9.5 to 10 volts when cranking and is normal, lower voltages are caused by weak, discharged, or under capacity batteries and excessive starter load caused by bad starter or effort required it turnover engine.

If there is a big differace, to isolate if the problem is on the ground side or the positive side I measure the voltage from the ground terminal on the starter to the negative terminal on the battery while cranking and it should be less than a volt. You then do the same from the positive of the battery connection to the positive post on the starter, should be lass than a volt.  That test is called a voltage drop test, it indicates how much voltage is lost in that circuit.

Also many coaches have a boost switch that ties the chassis and house batteries together to help with providing cranking power.

Another thought is the cable connections, some engines use 2 parallel cables from the positive and negative  connections at the battery because of the length of the cables from the battery to the starter, parallel cables reduce the loss because of resistance in the cables. Perhaps one of the connections at the batteries is incorrect like tied to the wrong battery bank if they are in the same compartment.

Title: Re: Slow Crank
Post by: Brett Wolfe on January 31, 2018, 06:59:29 AM
From: Dave Atherton
Date: Wednesday, January 31, 2018
Subject: Re: [DieselRVClub] Slow Crank
To: DieselRVClub
Check chassis and house battery voltage. A fully charged battery charge level is 12.70 volts. A fully discharged battery 11.90 volts, the drop in voltage stated  when cranking is not falling into the correct window as far as cranking power is concerned.  The combined starting ( chassis and house batteries should over come low voltage provide voltage higher than 12.32 volts. )  Going back that battery voltage voltage is 12.70, than looking at battery cables and connections some have lead clamp with bolt and come have a copper end with hole. Connections clean and tight. Next step move to starter 12 volt cable going to starter solenoid is the connecting stud tight on plastic end on solenoid than are cable ends tight to solenoid. No we go to ground stud on starter end clean and tight, is ground cable connect to frame clean and frame clean with good faster. Ground cable going to engine block. Grounding to block many over look this area because thinking starter is bolted to block this is incorrect thinking.

Last checking starter and solenoid after turning engine over for 30 seconds for heat is the starter or solenoid warm. If starter is warm your starter is the problem or clicking or click sound solenoid is the problem on engagement of magnet to connects.
Title: Re: Slow Crank
Post by: Vorlon on January 31, 2018, 11:58:54 AM
Thanks for your reply.

The cables on the battery terminals have all been cleaned and indeed the connectors to the solenoid (which is new) and all connectors to the starter (which is also new). There are about 4 or 5 connectors on both neg and pos of the starter. What i did not realize is that the starter negative also connects to the frame and the block so those connections have not been cleaned. This may well be the problem. I had assumed by using a good jump connection direct to the neg starter motor connection (it is too tight to connect the positive starter to the cable) I would be at least sure of a good ground. Perhaps there is a loss of power at the frame or block due to bad connections. I will not be able to do much for the moment mas we are inundated by snow and no real sign of increasing temperatures for the moment.

As soon as I can I will test and post back here.

Thanks again for your help.



Title: Re: Slow Crank
Post by: ziggyh on February 01, 2018, 11:50:54 AM
Might be worth mentioning that 12.7 volts is for a battery at 78 deg F for ocv test, (open circuit voltage) test and that voltage will be about 12.5 with a battery temperature near 32 degrees F and drops a bit more with temperatures getting into the -20 plus range.
Title: Re: Slow Crank
Post by: David.e.atherton on February 02, 2018, 05:26:35 AM
Vorlon, reviewing all your post on slow cranking engine and many good post reviews.
I take it you live in the cold climate and it’s is very cold outside when trying to start your
motor home. Your problem with slow engine cranking is related to thick oil that needs
or be warmed up with plugging in engine heater if equipped, or get heat under engine.
Caterpillar HEUI injection systems require warm oil, your injection system is operated
with high pressure engine that takes 870 psi to start engine than goes to 4000 psi after
startup. Good indication with very cold engine oil is what is called the buzz test with key
on. What happens under the valve cover, you can hear a buzzing sound from each
injector in firing order from the engine ECM. This is what is called with HEUI injectors
electrical operation allow movement inside of injector to warm  oil within the injector.
High pressure HEUI pump with the accumulator with cold oil will create drag on engine.
In closing many good post have covered your problem but it is now down to warm
Weather or heat applied to your motor home. Do not use starting fluid in any way to
assist in startup because damage will happen . Reply from Ask Dave, Dave Atherton
Retired Cat Mechanic
Title: Re: Slow Crank
Post by: ziggyh on February 02, 2018, 11:29:17 AM
On  a side note. I added an Espar engine coolant heater to my c9, we camp out into November in freezing temps and head South in the beginning of January. This years ambient temp was -32 and with out the engine heat I'm sure I'd still be in Winterpeg. The heater is one of my best additions for cold weather starting. I had contemplated the Either kit from cat but still kind of old school on either startups even with the lube added to the either.
Title: Re: Slow Crank
Post by: Brett Wolfe on February 02, 2018, 01:29:03 PM

Would not even consider ether with any engine with intake manifold heater (which is most engines today).  Somehow shooting ether onto red hot wires sounds more like a death wish than desire to start an engine.
Title: Re: Slow Crank
Post by: ziggyh on February 02, 2018, 03:08:12 PM
I do understand that, I believe the cat kit is actually programed into the ecm and it disables the intake air heater and is plumed into the intake manifold with a nozzle.
Title: Re: Slow Crank
Post by: WILDEBILL308 on February 03, 2018, 07:30:40 PM

Like I posted earlier I still think the OP needs to turn on his engine heater for 4-6 hours (depending on how cold it is) before trying to start it.

Bill, you are 100 % correct thank you. Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Slow Crank
Post by: Brett Wolfe on February 04, 2018, 06:39:38 AM
Yes, a number of good ideas here-- lets summarize:

Check voltage at the starter while cranking-- better to be around 12 VDC, but above 11.5.  Both starter and intake manifold heater are high-amp draws.

Check voltage at the batteries while cranking to compare with reading at starter OR check voltage between starter positive lug and battery positive terminal. Any voltage reading more than a few tenths lower at starter indicates RESISTANCE that needs to be identified and eliminated (clean and tight connections, cables in good condition (not oxidized= shiny copper, not green powder).

And absolutely in very low temperatures, run the block heater for a couple of hours.

Let's wait for the OP to do these things and get back to us with his findings.