urgent help please

Measuring the voltage on the starter solenoid wire, while it is disconnected from the solenoid, does not tell you anything about what resistances you have along the wire coming from the key switch as there is no current flow through it. The resistances cause voltage drop only when the current starts flowing through them so you can measure say 12.2 V on the disconnected solenoid wire but it will drop significantly below that when that wire carries current. Starter solenoids take some 20-30 Amp to engage and, depending of the amount of resistance, the voltage can drop to even less than half of the actual battery voltage.

In my case (348 tb) the problem was in the 9-pin connector at the left side of the engine compartment through which the starter solenoid wire (thick white) goes. Its pins were corroded causing intermittent no-start.

 

Hi Mike,

The explanation why the 348 solenoid is "picky" about the voltage is because 348 does not have a starter relay and most other cars have. Inserting a starter relay into the wire from the key switch to the solenoid is a good idea.

 

ohms law current equal voltage /resistance squared

voltage is useless by itself, you have to have current to energize the coil therefore the less resistance the better

 

Can you give me a couple of examples of common cars that actuate the starter solenoid through a relay?

 

So, in other words, what I said...

 

Mike,

My Jaguar and three BMW 7-series, all from the 80's, all had starter relays. My (current) 1998 Saab 9-5 also has has one. The diagram shown is for a 90's Volvo.

 

aa
Image Unavailable, Please Login

 

Peter, one of the most common solenoid failure modes is a heat related open circuit in the winding (or internal connections), or the insulation on the windings breaking down due to heat, causing a short. Often in those cases tapping on the solenoid with a wooden hammer handle or the like will cause the solenoid to actuate. The preferred method in this situation is to have someone hold the key in the start position and then tap on the solenoid itself, firmly enough to jar the connection, but not so hard as to dent the solenoid housing.

The fact that the solenoid has engaged repeatedly subsequently suggests the possibility (but by no means assures) that the solenoid is failing internally. If indeed that is the case, adding a relay will not help, although the above method might save you the cost of a flatbed.

I have tried to keep my replies simple and practical, and will do so here again. Now knowing what a strict adherent the 348 solenoid is to Ohms law (ahem), I intend to add the relay kit to my own car and would suggest the same to any owner. Or, if you're needing a short term solution, you could fabricate a simple jumper by soldering a female connector that will fit the solenoid onto a short length of 10 gauge wire and paring back a few mm of insulation on the other end of the wire. If you want to get fancy, tin the exposed conductor with solder. Toss that in your glove box or tool kit in case you ever need to jump the solenoid again. It's a little safer than poking around the high current lead from the battery with a screwdriver (which works just as well, but can get exciting in a hurry if you happen to touch the screwdriver to the battery lead and ground at the same time). Whether you install the relay or just want the ability to jump the starter if the need arises, the end goal is to provide full battery voltage to the solenoid instead of relying on the potentially resistive lead from the keyswitch.

But if I were in your shoes I'd go one step further (assuming I didn't just replace the solenoid for good measure). I'd also make sure to have some means of tapping on the solenoid in the event that the root cause turns out to be a heat related internal failure. It doesn't work in every instance, but in my experience it works at least half the time, so if it were my car there would be some means of tapping on the solenoid available until I was reasonably sure that the problem was solved.

Just my own two pence, for whatever it's worth. I don't claim to be an expert on Ferrari electrical systems-- heck, I was very surprised to find how sensitive the solenoids are to voltage when most other cars will engage the starter even when battery voltage has fallen too low for the engine to start. So I learn plenty from these pages, but I do have a little background in automobiles, having owned a multi-marque repair shop for many years and now being in the business of preparing production based cars for track and road racing.

Best,

///Mike

 

'80s Jags and BMWs are both cars I've worked on quite a bit but I confess I have no memory of starter relays on either. Then again, my memory is often notably bad, and I'm not in front of either computer that contains wiring diagrams. One thing is for certain, the diagram you provided does show a starter relay. Then again, the car in question is a Volvo.

In any case, there are a great number of cars out there that do not have starter relays and will still engage the solenoid when the battery voltage is too low to rotate the engine more than a couple of turns.

But we're straying somewhat afield of the presumed goal of helping Peter resolve his no-start issue. In the end, whatever the reason, adding a relay to the solenoid actuator lead is advisable on a 348. Agreed?

 

Micky, as an example of how bad my memory is, it just dawned on me that cars with inertial starters have relays, since a solenoid is not needed to engage the Bendix.

Best,

///Mike

 

Had the same problem in my 1990 348. Here is the solution:

Amazon.com: Bosch WR1 Starter Relay: Automotive

 

Yes, I will also add one to my 348. Although I have not had a problem since fixing the 9-pin connector, I will put it in to prevent the problem and to save the key switch contacts. I prefer to use a bit more robust relays than the standard cube type, like:
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Any idea how much current the solenoid draws?

 

Good pictures here. http://www.ferrarichat.com/forum/136967618-post12.html

 

The starter solenoids draw, in average, some 20-30 Amp to engage (pull-in coil), thereafter about 5 Amps (holding coil). The pull-in current is difficult to measure because it only lasts for a split of a second, from turn-key to the start of motor rotation.

Some older starter solenoids (like the Lucas on my ex Triumph Stag) draw as much as 70-80 Amps to engage.

 

Hi Peter

I wrote some instructions and took some pics when I instaled mine. Never had a problem starting since

Bosch WR-1 Hard Start Relay Fitting

 

I use rockauto quite a bit and they do deliver very quick.

IIRC when originally looking this kit is used a lot in volkswagon camper vans????!!!!! LOL

 

Thanks!

 

The website is down, anywhere where the instructions and pictures can be found?

 

For the Bosch WR-1? there are 2 threads I have seen out there, One is more complicated that it needs to be and one is simple install in engine compartment.

 

Hi Guys

I'm afraid that 348manual website suffered from the photobucket ransomware!!!

Anyway, the threads on my original posts are below: (its plit into 2 as I'm usually doing more than one job at a time so bear with me - its why I tried to put it on a website in a more organised fashion.

Just a note I did this mod nearly 7 years ago and the car still starts prfectly each and every time whereas orior it was all a bit hit and miss so definitely worth doing and cheap too

https://www.clubscuderia.co.uk/forum/showthread.php?45388-348-DIY-quot-Restoration-quot&p=747316#post747316

https://www.clubscuderia.co.uk/forum/showthread.php?45388-348-DIY-quot-Restoration-quot&p=749743#post749743

They sell them from rockauto.com - just put Bosch wr1 (don't use wr-1) and it comes up there for about £20 or just google bosch wr1 - again no dash in the wr and 1