Start Assist

[Chuckles]

The 'Start-Assist' on my 1982/3, 310 didn't come on yesterday. The first time I needed it in earnest (radio left on!). I always try it every time I start the engine just as a check.

It is the separate button type not an automatic start relay. I think I may have disturbed a wire or two but my question is, does this circuit have a fuse? I cannot find any reference to a voltage source for the assist button on the drawings that I have.

In addition, does the wiring follow any standard colour code that can help in tracing the route to follow? I tried to trace the wiring but it was "lost" in the bird’s nest under the dash.


On the switch it looks as if there is just one black and one white wire. The white is then crimped to a yellow. The Black disappears to the front I think to the isolator, but not sure, the other white, then yellow, goes up in the dash wiring above the AC plenum.

I have searched two manuals (1982/3 and 1984/7). The later one mainly refers to the automatic switching, but there is only just a scant referral to the solenoid by the batteries only.

Any guidance will be gratefully received. This is a great collection of forums for sorting out our little problems….

Thanks
Chuck

[swebster]

Chuck,
Mine is setup with a momentary switch in the glove box which energizes a relay (solenoid) near the batteries. This connects the house batteries to the chassis system. You can test it if you find the solenoid by energizing it locally. This solenoid should be mounted somewhere near the batteries. The positive house system should run through it.

[Chuckles]

Steven, I found the solenoid, But it doesn’t engage. I am suspecting the power source to the solenoid, from the button, or indeed the power to the button - wherever that comes from!

It would seem strange that such a circuit would not be fused, hence the question. There just doesn’t seem to be one in particular as I can find, but as I ran short of time yesterday I cut short the search.

I think I will be going back to my original thoughts, in rewiring the under dash area as there has been many modifications, additions and take away’s.

Thank you for your help on this.
Chuck

[ralley]

I think your fuse issue may be a red herring, as the fuse in the system would be the main ignition fuse, which is easily checked in the automotive fuse box. Since the switch/button is in the positive circuit, you should have voltage to one side of the switch when the switch is open and both sides when closed. If the switch/button works properly, then suspect the solenoid and its connections near the battery box. You can jump the solenoid from a good battery--a solid "click" is a good sign--when the solenoid, which is also in the positive circuit, shows voltage at all studs, it is probably working properly at joining your batteries.

At the risk of stating the obvious--check your grounds.

Rob

[swebster]

Try connecting the solenoid at the terminals on the block. If you hear it "click" then you'll know its fine and to look upstream.

Chasing wiring gremlins is no fun

[Chuckles]

Found it!; Found it! Found it!; Found it!

By pure luck.... The 12 volt socket by the dining table, that also houses the TV antenna socket, was dead, so ..... I checked the fuses at the 12 volt distribution panel by the fridge.....

The only one blown was the Second fuse down, circuit 2, yellow. This fuse also protects the 12 volt sockets AND the Start Assist button.

Another piece of usefull information to add to the book!

Hope this helps

Chuck

[swebster]

Well done! Sometimes you get lucky on these things. It goes along with my father's advice...always check the simplest thing first. It's amazing how many times he's been right over the years.

[Chuckles]

Hi I am Back.....

Yes; ... well the fuse is now a major problem. It blows when nothing is switched on. It may blow after a couple of days or as in today after a few minutes.

I isolated each circuit in turn that fuse 2 (Yellow) covers, so it says in the book, if you believe that. The yellow power wire from the fuse shows an almost dead short to ground. I thought I found it with the antenna circuit, the bedroom clock, and the wiring under the dash for the entertainment/CB, which I don't have, but no.


My only recourse left appears to be the start assist solenoid. I started the engine, (by jumping to the coach battery sets) it showed a charge, but the chassis battery must be dying fast as it only gained 12.15 volts after at least 1/2 hour running. So on a restart, I hit the start assist button and seconds later? ....fuse blown.

Question.... Is this solenoid powered all the time and the start assist button completes the circuit by grounding the -VE side of the solenoid. It is about the only thing left that I can think of (apart from tearing whats left of the hair out ) It could account for the random fuse blowing as the current across the solenoid increases or is above 35AMP (yes that was the last fuse used 35 AMP!)

I have come home short of food, breath and patience!

Please can any one shed some light on what has become the most annoying intermittent fault I have known for years!

[Chuckles]

OK; I have had another shot at this and now I have narrowed the problem a little more and all courses point to the Start Assist system.

Definitely the Start Assist relay is powered from the #2 yellow 12VDC house circuit. It looks as if it was a convenient wire to use, as it is 'up-front' feeding the entertainment centre and CB, according to the wiring diagram. The ground side must go through the case as there is no separate terminal for ground (-VE)

I am proposing the following and would appreciate any comments.

Take the feed wire to the Start Assist solenoid directly (with or with out a fuse) from the terminal on the starter solenoid, that, when the starter is activated, connects the engine battery power on the starter solenoid to that out put terminal. Use the Start Assist button to send house battery power to the start assist solenoid, via a relay.

What I am hoping to achieve is
1; Automatically calling on the house battery to help the starter every time. I understand this happens on later models.

2; Have the ability to give the start assist solenoid power from the house batteries should the chassis battery be too flat to even pull in that solenoid.

My big question is ... does any one know what amperage the start assist solenoid pulls. At present it will blow a 35amp fuse, and then that circuit stays grounded for a few minutes after, so question 2 ... do you think the solenoid is shorting out inside, by the heat build up, in other words has anyone had trouble with these solenoids breaking down that way.

Any thoughts on this would be very welcome. We are due to go away for a few weeks - Boone-docking - I think it is referred to so I must have this sorted before we go......

Thank you for indulgence

[ralley]

"What I am hoping to achieve is
1; Automatically calling on the house battery to help the starter every time. I understand this happens on later models.

2; Have the ability to give the start assist solenoid power from the house batteries should the chassis battery be too flat to even pull in that solenoid."
(quote)

If I understand you correctly, you will frustrate the intent of the start assist, which is to keep the house batteries isolated from the starting battery UNTIL a joining of the battery banks is required in case you have a low starting battery, like when you leave the radio on.

A routine automatic joining of the batteries is a lousy idea, because it will someday leave you sad and lonely--a low battery anywhere in the system will draw down any charged battery to which it is attached. Later models, at least, have a paddle switch in the glove box which must be held in place to join the battery banks--if you release the switch, the switch opens, breaking the circuit. It is a reasonable fail-safe system.

1. I think my first step would be to remove and test your push-button switch. Not the most likely culprit, but useful to eliminate as a cause.

2. My next would be to remove and test the solenoid. If the ground for the solenoid is/are the bolts which hold it in place, test the ground off and on the vehicle. Clean up the bolts before you reinstall them.

3. Isolate all the other stuff on the circuit which blew the fuse and use a jumper with alligator clips to attach to a different 12V circuit. If it works without blowing the fuse for that circuit, then your solenoid guess( or some wiring nearby) was probably right. If not....we shall see.

Rob

[Chuckles]

Rob Thank you for your interest in my problem and your valued input.

I think, but not sure, that we might be a cross purposes, but I stand corrected if I am wrong.

The idea of using the starter solenoid contact points was that the house batteries were pulled in as the starter solenoid hits in. The disc that makes contact from the battery input to the starter motor also hits another contact. This contact is the one I referred to. This will be the only time all batteries are in circuit.

Now if you say this is bad practice, I accept your point. Nothing is worse than what I call a mop-and-bucket operation. In other words, clean up the mess but don't fix the dripping tap!. Yes; the battery is dying and needs to be changed now, but this is a good exercise to pre-empt a situation where, as you say, the chassis battery may go down if some things are left on.

Perhaps I should think along the lines that I keep this idea, but have an interlock switch (Use the push button) so if the extra boost is not needed, then don't use it! By using the starter solenoid contact the house batteries are only used momentary, whereas just using the button on its own some times that can be engaged for longer than necessary. Using the starter solenoid was the reasoning behind the question of current draw.

I have done as you suggested in testing each item on the circuit in turn, and the start assist part definitely gave clear indications of a problem.

As I see it, the heat generated in the coil of the solenoid causes the coil to expand, which then may be shorting out say on the case. The fact that after the fuse blows, the circuit is still in short for a few minutes indicates that the short may be caused by heat and when the coil cools it eventually ceases to be touching the case - or what ever.

Would you think that is likely?

I am very nervous about touching the solenoid until I have a replacement at hand because it appears to be quite rusty around the terminals. I will try again tomorrow after dowsing it all in copious amounts of WD40 and take it from there

[ralley]

I think you are right--we were at cross purposes. I was confused by your proposed starter solenoid wiring--I was refering to your solenoid (you referred to it as a relay) which parallels the battery banks, joining both the starting and house batteries BEFORE the starting solenoid. It is possible that you no longer have this circuit, BUT YOU SHOULD HAVE IT!!

1. Perhaps I can make this more transparent: The SWITCH which is activated by your start assist button, and joins your battery banks, is my best candidate for being at fault--you should test this switch both on and off the vehicle, isolated from any wiring, if you have one.

2. You should also test your starter solenoid, both on and off the vehicle.

3. One of the two, perhaps both, are most likely the fault. I would guess that your burned covers and such around your starter/starting solenoid is likely to be the result of excessive cranking, but it is not necessarily an indication of a failed starter solenoid--not yet, anyway. But the burned cover/contacts/fragile wiring indicate that you are close to the problem.
By they way--I burned all the insulation off the ground wire on one of our old Benz sedans last weekend trying to start it. Please check out your battery cables if you have been cranking a lot.

I still think that wiring the starter solenoid in the manner you indicate is a recipe for disaster. As I see it, if wired directly, a failure of the starting solenoid or starter (under some circumstances) could cause all your batteries to fail, or cause a fire (excessive amperage draw= heating), or both--a really catastrophic failure. In a system with a switch/solenoid parelleling the batteries only on demand BEFORE the starting solenoid, both the switch and the staring solenoid would have to fail, simultaneously, and both solenoids/switches would have to remain closed for a catastropic failure to happen.

I should think that the switches/solenoids in question, if they need replacement, should be easily obtainable in GB, or from Canada. They should not be very expensive, given the sad state of the US Dollar.


Rob

[garry]

My thoughts:
The solenoid for starting boost is at fault as you suggested however; If it worked before as designed you would be better of repairing instead of reengineering. The solenoid that connects the house batteries to the chassis battery is not a high dollar item and is not unique to RV's.
Also if you replace the start battery with a good one your need for the assist may be not needed until you can find the replacment solenoid.

Garry

edit for spelling

[Chuckles]

I have returned from the beast a happier person!

Leaving it to be the last of all items tested, I can confirm that the start assist solenoid had the fault, with a near total short to the casing.

Using a standard free standing starter solenoid the circuit was reinstated and many starts, with and without the starter connected, proved the point. NO BLOWN FUSES!

I will give it a couple of days, so if you don't hear any more - It's sorted...

Just as a recap for reference:

1: The #2 fuse on the Yellow 12vdc circuit kept blowing, which also disabled the Start Assist Facility, for apparently no logical reason.

2: The symptoms seem to have started after a lengthy cranking on the starter when an air lock happened in the pipework or fuel evaporated in the feed pipe or in the carburettor, after a rest stop on a very hot (for us 35 degrees C) day.

3: After this time some 12 volt facilities were not working and traced to the # 2 Yellow circuit fuse in the 12 volt fuse panel. Replacing this fuse coincidentally restored the assist start, thus proving the route and source of the power to the solenoid. The integral starter solenoid also had damage to the end cap and burnt wire to the crimp terminal, possibly due to excessive and rapid heat build up during the cranking.

4: The complex nature of the fault was that after the fuse had blown, the circuit stayed in fault for some time after, which could be attributed to the solenoid cooling down releasing the short. There were also other-times the fuse would blow for no apparent reason - possibly now in hind site, it may be the temperature differences between the hot day air and cool night breezes blowing under the Airstream.

Hope this helps, and a big thank you to every one who submitted very useful tips on tracking the faults. I do appreciate every body's contribution - every little helps no matter how trivial it may seem at the time - it ALL adds up

[ralley]

LOVELY!!!!!
However:
"2: The symptoms seem to have started after a lengthy cranking on the starter when an air lock happened in the pipework or fuel evaporated in the feed pipe or in the carburetor, after a rest stop on a very hot (for us 35 degrees C) day." (quote)

When you run out of things to do, check your fuel pump and fuel lines, including the fuel filters where fitted! 35 degrees C is hot anywhere, but......it should not have happened. A strong fuel pump pushing fuel through good fuel lines will not allow evaporation. It is supposed to be a closed system--so there is no where for the fuel to go except into the carburator if all is working properly.

No rest for the wicked?

Best,

Rob

[ROBERTSUNRUS]

Hi, Chuck. I have a few more things for you to think about; Starter and assist solenoids [basically the same thing] can and will stick in the on position usually when overheated. This can happen more when you have weak or bad batteries that won't hold a good charge. Weak batteries, under heavy load such as starting an engine, create higher amperage. This is too much for the solenoids to take for very long. Replace the known bad batteries and the overheated / sticking solenoids.
Next, the fuse is doing it's intended job by blowing from overloaded circuits. I did not see what the size fuse was originally in that circuit, [maybe 20 amp] But never go to a higher amp fuse. Basically, if you have a 20 amp circuit, you have a 20 amp fuse and 20 amp wireing. I personally have repaired many vehicles who's wire looms have melted and or burned up because the fuse was upped or bypassed. If the fuse is blown, a larger [higher amp] fuse will not fix the problem; And in a lot of cases, will make problems a lot worse.

Bob

[Chuckles]

Rob I take your point, however I was not thinking too clearly at the time - panic set in....

The saga at the rest stop started (or not as the case may be), when initially the engine started OK, but then, moved about 15 feet out into the way of oncoming traffic then stopped. I thought, mistakenly, that blipping the throttle I had flooded the carb. All this so far on the mechanical pump.

Thinking the carb to be flooded I floored the throttle - as you do - and kept cranking. THEN I THOUGHT! .... Perhaps......

Soooo...with the aid of an override switch that brings in an electric fuel pump .... need I say more.

Of course THINKING AGAIN it is along way for a mechanical lift pump on the engine to pull the fuel some 25 feet away. So now the electric pump is put to good use ..more often!

Bob, Yes I agree increasing fuse blowing amperage is not good practice, and yes I was silly to that, but at the time desperation and the lack of 20 amp fuses forced the issue a bit. It also made me realise this was not going to go away - silly me thinking that it may be a bit of damp or whatever, but One does tend to 'grasp at straws' in desperation.

Perhaps I should stop thinking! ............. Wrong! Think more - act later!

And before any one notices ..... the new battery is on order! I say order because the side connection type are hard to find here.

[Chuckles]

Originally Posted by ralley

LOVELY!!!!!
When you run out of things to do, check your fuel pump and fuel lines, including the fuel filters where fitted! 35 degrees C is hot anywhere, but......it should not have happened. A strong fuel pump pushing fuel through good fuel lines will not allow evaporation. It is supposed to be a closed system--so there is no where for the fuel to go except into the carburetor if all is working properly.
No rest for the wicked?

Rob, I think you may have opened a can of worms on the fuel bit.

I am sometimes aware of the smell of petrol, although not quite so much now the weather is cooler. It is apparent more the drivers side than the passenger, according to 'er in doors - The Boss - Seat Cover - Yes... OK Mary MY wife!

It is only noticeable when altering the throttle movements (in traffic, up hills, or overtaking). There are no signs of fuel leakage or flooding/overflows at the engine/carburetor end.

I think (Scrub that; no thinking!) it may be to do with tank breathing. The fuel filler is way back at the rear so it cant be that, but I was informed that on some coaches the tank vent goes up over the wheel arch some where, and travels up to the front terminating in a canister (Carbon activated?) This I have yet to find.

I do intend to replace all the flexible fuel lines from the rear in Copper or steel, when I do the LPG conversion on the engine, as I am sure if it is rubber based the hose must be aged by now, but as mentioned there no signs of leaking.