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Wtf is happening

Han-Tyumi

New member
Joined
Apr 21, 2017
Location
Spanish Fork, UT
Okay, so to start this off:

Lately my 1987 745 Turbo has been "hiccuping". Sometimes on idle it will just stop firing for half a second and run fine and then "hiccup" again, etc.. Only recently has it started doing it under boost, but only at freeway speeds. Say I put my foot down to pass; it sort of sputters and has a little bit of a hard time building boost for a second and then will be okay after it's moment and I can be in boost for as long as I'd like, until I slow back down and try to pass again.

Today on the freeway, on my way back home in a terrible snow storm, it stopped letting me give it fuel. Out of nowhere, it just sort of stopped the input of my pedal and slowly went down to 1000 RPM and then turned off and wouldn't start. Luckily, I had time to get to the shoulder. I popped my hood to see if anything was out of the ordinary, no go. I tried starting in limp mode "MAF unplugged" and no dice. I let it sit for a few seconds and it starts for 1 second and turns off again. I thought maybe one of the fuel pumps died. I double checked my ignition and air. No visible leaks, and I did a full ignition tune up about a month ago. So I get towed (which took 40 minutes for him to arrive and then 3 hours to get home due to the length of the journey and the terrible storm).

My car has been a bit of a nancy at times, acting funny for some period of time and then magically fixing itself, so I wondered.. Will it start now that it's home and I had gotten it towed for an outrageous amount of money.. Of course it does, and it drives too. As if nothing happened.

I don't know where to begin. The "hiccuping" issue has been happening for awhile, but seemingly fixes itself for weeks and comes back randomly. I will also note that my battery failed a test back in June, but hasn't ever had a problem climbing back up to 14 volts on the gauge in the cluster. Now that it's gotten really cold though, if I turn my headlights on in the morning none of the cluster lights work, no analog clock function, no speedo, no rpm gauge, no fuel and it shows the hazard lights stuck on, until it climbs back up to around 11 volts, then everything springs to life. I'm not sure if it could be my battery making things act weird, but I'm getting sick of it.

Any recommendations?
 
Okay, so to start this off:

Lately my 1987 745 Turbo has been "hiccuping". Sometimes on idle it will just stop firing for half a second and run fine and then "hiccup" again, etc.. Only recently has it started doing it under boost, but only at freeway speeds. Say I put my foot down to pass; it sort of sputters and has a little bit of a hard time building boost for a second and then will be okay after it's moment and I can be in boost for as long as I'd like, until I slow back down and try to pass again.

Today on the freeway, on my way back home in a terrible snow storm, it stopped letting me give it fuel. Out of nowhere, it just sort of stopped the input of my pedal and slowly went down to 1000 RPM and then turned off and wouldn't start. Luckily, I had time to get to the shoulder. I popped my hood to see if anything was out of the ordinary, no go. I tried starting in limp mode "MAF unplugged" and no dice. I let it sit for a few seconds and it starts for 1 second and turns off again. I thought maybe one of the fuel pumps died. I double checked my ignition and air. No visible leaks, and I did a full ignition tune up about a month ago. So I get towed (which took 40 minutes for him to arrive and then 3 hours to get home due to the length of the journey and the terrible storm).

My car has been a bit of a nancy at times, acting funny for some period of time and then magically fixing itself, so I wondered.. Will it start now that it's home and I had gotten it towed for an outrageous amount of money.. Of course it does, and it drives too. As if nothing happened.

I don't know where to begin. The "hiccuping" issue has been happening for awhile, but seemingly fixes itself for weeks and comes back randomly. I will also note that my battery failed a test back in June, but hasn't ever had a problem climbing back up to 14 volts on the gauge in the cluster. Now that it's gotten really cold though, if I turn my headlights on in the morning none of the cluster lights work, no analog clock function, no speedo, no rpm gauge, no fuel and it shows the hazard lights stuck on, until it climbs back up to around 11 volts, then everything springs to life. I'm not sure if it could be my battery making things act weird, but I'm getting sick of it.

Any recommendations?

IBCI
 
Seriously though. Your battery failed a test in June and you haven't replaced it yet? (or at least gotten a second opinion?)

Don't you think you should start with that?

BTW, the voltage on the gauge doesn't mean $#!t. If anything it is showing you what the ALTERNATOR is putting out. And, 14 is too low. Should be 14.6+

The car won't run below 11 volts (well it might with EVERYTHING turned off.)
 
Actually a bad battery can cause a low reading when testing the voltage while running.

So, you can disconnect the ground for the battery after you get the car running and test the alternator output that way. Should be 14.6 or more (on a multimeter - not your gauge in the car).
 
A bad cell in a battery can cause a lot of weird issues. I would definitely look into that.

I think 14.6v is a little optimistic from the alternator. 13.8v and higher is considered "normal".
 
Meh. I forget about 30 year old parts designed for a car with minimal electronics.

ftfy. 13.5-14 is pretty good for a stock 240 while running accessories like radio, headlights, ac, blower motor. I noticed more voltage with everything running after i switched to a sensor 100amp.
 
A bad battery can cause excessive load on the charging system which in turn will upset the electronics.

Put your battery on a battery tender overnight then have the battery load tested.
That is the only way properly test a battery.

Then you can move on to the next level of diagnostics.
 
ftfy. 13.5-14 is pretty good for a stock 240 while running accessories like radio, headlights, ac, blower motor. I noticed more voltage with everything running after i switched to a sensor 100amp.

You should be testing the battery with all that stuff turned off.
 
I guess I am spoiled.

I have been using this shop for (nearly) my entire adult life...

Every single Bosch alternator rebuilt by them put out 14 volts or more. I would swear they were all closer to 15 but it has been a while since I've even had my hands on one, so...

FWIW, I know that the 100A Bosch rebuilt by Southern Armature (and properly shimmed to run on my b230ft) ran at 14.6. It also ran an OEM Bosch regulator. YMMV.

Anyway, batteries rarely (never, excepting low fluid cases - even then...) test bad and then suddenly function properly. So, this is where the OP should start.

Edit:// I also had (have - not in use) AutoMeter gauges (voltage, vac/Boost, oil pressure) but even then... only used them as relative measurements against calibrated Technicians gauges (or my Fluke in this case).
 
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PS. Voltage drop issues are normally bad connectors or corroded wire and can usually be found with a decent DVOM.
 
Check the fuel injector relay and the wires leading into the connectors. This happened to my old 240 - I must have pulled the relay out by the wires instead of the connector, and one of the leads wasn't seated properly in the connector. Pushed it back in and my weird intermittent problem (just like yours) went away.
 
Does the 7 series still use the goofy euro bullet fuses? I had a few of those fo bad on my 245, the aftermarket plastic ones just can't handle the heat at the contacts. I raided a pile of the ceramic ones out of a Mercedes at the junkyard, and that fixed a lot of odd issues.
 
So, I tried to start it again this morning and it wouldn't. I guess it was just lucky when I started it after it got towed.

I went ahead and replaced my battery, but it didn't fix my issue. Fuel pumps are operating, injector relay, wiring, fuel pump relay, fuse, etc all good.

When I try to start it, it will still do the same thing were it fires for like half a second and then goes back to cranking. Hall effect sensor maybe?
 
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