Allison (Crane XR-700) Troublshooting

[ctaylor738]

Everyone remember that I bought this car ('72 250C) on e-Bay, completely disassembled, and that it last ran in 1988. I now have it back together to the point of trying to start it.

The ignition was been replaced with an Allison XR-700 unit, which I strongly suspect is an early Crane unit. I reviewed the posts and it seems to operate the same way.

It does seem to be installed correctly. Red to positive on coil, black to negative, purple to ground. The detector block seems to be positioned correctly.

I am getting 9+ volts out of the pre-resistor, and 4.75 volts to the coil which means that the XR-700 would also be getting 4.75 volts. The coil is a new Bosch unit.

The original CD unit seems to still be installed, but it is completely out of the loop.

I am getting no spark out of the coil whatsoever when cranking.

Suggestions from you XR-700 guys?

My questions:

Should I set the dwell as per the instructions and posts? Even with the dwell out of adjustment, I should still get something out of the coil, yes?

Is there a check to see if the unit is working at all?

Did I buy the wrong coil by asking for the replacement?

Thanks.

[Jim Villers]

I suspect that you have two wires reversed. You can read the installation instructions on the http://www.cranecams.com web site or check the full link:
http://64.90.9.168/cranecams/pdf/90002000a.pdf

It says that the black lead goes to ground, yellow to coil ground and read to coil positive. I suspect that your purple is the same as their yellow.

You can test it by turning the key on and rotating the distributor (with the cap off so you can see the slots) and the coil high voltage wire connected to a grounded spark plug (use a plug wire from the coil to the plug). Hard to describe but easy to do.

Good luck.

[Arthur Dalton]

XR-700 series Cranes call for a standard coil.
You may have bought one with internal ballast.
Check resistance from coil + to - terminals.
If it is around 3 ohms, it is the wrong coil.
[Most say on the side .]
Also, go direct from the pre resistor to + coil
and try it . The XR units are looking for 9 v.,
not 4.5
I have the triggering info test here somewhere if that does not do the trick, which I can send you jpg.
Arthur

[Arthur Dalton]

XR-700 series Cranes call for a standard coil.
You may have bought one with internal ballast.
Check resistance from coil + to - terminals.
If it is around 3 ohms, it is the wrong coil.
[Most say on the side .]Looking for < 1 ohm
Also, go direct from the pre resistor to + coil
and try it . The XR units are looking for 9 v.,
not 4.5
I have the triggering info test here somewhere if that does not do the trick, which I can send you jpg.
Arthur

[Arthur Dalton]

Here is Cranes XR Series "Trouble Diagnostic"
page:
http://members.aol.com/ajdalton7/xr700.jpg

Also,As the car sat in pieces for years, you may also want
to clean the LED's lens with a que-tip and some alcohol.
If the dist. sat around with the cap off, it may be simply dirt/oil on the optics.
Any other XR-700 users out there, feel free to make a
print. I will leave it for a week.
Arthur

[ctaylor738]

Thanks to all for the good info and quick response.

BTW - According to the documentation that came with the car, I do have it wired correctly - they seem to have changed the colors over the years. Probably printed in 1987 - pre Web! How did we exist back then?

Chuck

[DANTRCAV]

Chuck:

Arthur is correct. You need 9Volts to fire the optical trigger. If the coil you are using HAS internal resistance (check via Arthur's method) then you DO NOT want to use the external resistance. If the coil does not have internal resistance, then you use the external. As he also suggested, cleaning the optical unit is a good idea.

I have run both the original Bosch coil and a Crane aftermarket (currently installed) and both worked fine. I do understand that they have updated the system (I think the yellow coil(-) is the updated system which is the one I have) and made some changes in the control unit and optical window disks. When I used the Bosch coil I went from the .4ohm resostor to the .6ohm resistor to coil (+). The Crane coil came with its own resistor so I wired from the ignition point on the .4ohm resistor to the crane resistor thus bypassing the originals.

At $100 (max) per unit I might just spring for a new one just to get the updated electronics and eliminate any problems that may have been caused by the PO installation or whatever.

I am not sure about your voltage reading from your pre-resistor. I have the MB service manual on the stock ignition and it has the test voltages at all points, I will check it when I go home at lunch and post the test figures. Might be a problem in the resistors..

Dan

[Edited by DANTRCAV on 03-22-2001 at 08:13 AM]

[DANTRCAV]

Chuck:
Sorry I took so long - couldn't locate the manual. How is it wired from the pre-resistor reading 9v to the 4.5V at the coil? When I used the stock Bosch coil I went from the .4ohm to the .6ohm directly to coil (+) and I was getting 10.25V. Using the Crane coil and their resistor I get 11.25v at coil(+).

Check the resistance of each resistor and, even though it is new, if you have the correct coil it should read .35 - .45 ohms between the terminal (#1 and #15). You say the CD unit is completely out of the loop - double check to make sure you don't have a brown or black wire running back along the bottom of the fender well to the .6ohm resistor. If you do, the CD unit is not completely out of the circuit and that is a problem for the Crane Unit.

Another item, the Crane control box can get warm when then engine is running. WARM - like tepid water. If the unit gets HOT then it is receiving too much current - most likely a problem with the resistor(s)or coil resistence. When I talked to the Crane tech the one thing he cautioned me about was that the control box does not like to get hot and it is easily damaged.

If you can get at least 9V to the coil (+) you should have plenty of spark.

Hang in there..

Dan

[Arthur Dalton]

The Crane module seems to run hotter on the point
conversion systems with transistor ignition.
I believe the reason for this is that the coils on the transistor switchgear units is made to run at the lower voltage. That is why some who race these opt for the later coil.
However, for street driving, the early standard Bosh coil [230/250SL type] are fine and more compatable to the Crane units. They run much cooler and can be used with a standard resistor set-up.
Crane recommends elimination of switchgear, standard coil and resistor . No need for starter by-pass for starting.
Arthur

[Douglas Broome]

Has anyone heard reference to a significant writeup by someone named John Hassel (or Hassle) about the x-700? Where might I find this article?

[DANTRCAV]

Sorry, I have not.

Dan

[Arthur Dalton]

Originally Posted by Douglas Broome

Has anyone heard reference to a significant writeup by someone named John Hassel (or Hassle) about the x-700? Where might I find this article?

I saw it over at the 113 forum somewhere...
I think there is a post on it as we speak

[Douglas Broome]

I think that forum is where I came across the mention of it. Still, I am searching for the article itself. I want to see what it says about the Bosch black, blue, and red ignition coils, if anything; that is, a technical compare/contrast..

[Arthur Dalton]

I did some scope comparisons on them a few yrs back and found some interesting results
If I remember correctly, the blue has internal resistance/balllast, the black was good for street [ actually better than the Crane performance] and the
red was regected, but I don't remember why.. I think it was not oil cooled and ran hot.
I have the charts and info here somewhere and will report back...

[Douglas Broome]

I know that the Bosch blue coil is supposed to come with internal ballast resistance: nominally 3 ohms but accepted range, according to Bosch technical literature, of 2.4-3.3 ohms. That circumscribes its choice for applications. There is a lot of discussion in various internet fora about the blue coil(s)--(s) as seemingly there are several variations of the blue coil currently on the market.

The Bosch black coil comes with a sticker on it calling for an external ballast resistor of 0.9 ohms. Bosch technical literature in fact calls for external ballast resistance of between 0.6 and 1.0 ohms. Bosch TA tells me that the black coil is supposed to have zero internal reistance, but on another forum I read that someone had actually measured its internal resistance at 1 ohm. Unless the person got the wrong measuring result, I don't know what to make of this.

The red coil is also supposed to come with zero internal reistance. It comes with a sticker calling for external reistance of 1.8 ohms. Bosch technical specifications indicate a range of 1.4 to 1.8 ohms.

The Service Manual for my ponton Mercedes does not mention the phrase "ballast resistance/resistor." Where it discusses coils it does have a table called "series adjustment" and gives various values in ohms. Are these one and the same?