1.5 Diesel cutting out under acceleration - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• 1.5 Diesel cutting out under acceleration by Tmarkle on 24 Nov, 2017 22:22
• So I’ve recently gotten my little 1.5 bunny running. After getting the timing set, bleeding the injectors, and slightly modified intake and exhaust (no muffler) it pulls well at low rpm. It sounds nice down low but at higher rpm it cuts out, dims the lights, and a relay chatters loudly under the dash. It has a carter electric fuel pump and the glow plugs are now operated via starter relay and fuse block (pimp your glow plugs). I’m thinking that there is a voltage problem intermittently closing the fuel shutoff solenoid. Once I parked it tonight, I tried to restart it out of curiosity and there is no charge left. I’m hoping that this is one issue not two separate ones.
  
  
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• #1 by Dakotakid on 25 Nov, 2017 13:03
• Could be two problems: the brushes on the voltage regulator.
• #2 by ORCoaster on 25 Nov, 2017 19:31
• but at higher rpm it cuts out, dims the lights, and a relay chatters loudly under the dash.
  
  This speaks to me of a voltage generation problem, well more like a loss of voltage generation.  Such that your battery was depended upon to supply a load that it might not have been ready for.  The loss of voltage at the solenoid is critical to keep the engine going right?  I am not sure just what critical voltage is needed to do that.  10.5?  Will that be enough to hold it open?  The relay under the dash is a head scratcher for me.  Unless it is the one that controls the intermittent wipers.  That one is the only one that makes noise in my two VW's.  Just a click before the wipers move.  Maybe the one relay that controls the seatbelt/key chime/warning light.
  
  I would be looking to service and possibly repair the alternator.  Starting with the brushes as noted prior by Dakotakid.
  
  Let us know your voltages prior to and after repair.  Dielectric grease on the terminals is good to do.
  
• #3 by Tmarkle on 25 Nov, 2017 21:07
• https://youtu.be/H-A3IEE76Xk
  Here’s a video of the issue. My battery tester shows no charge from the alternator. There is some questionable wiring in between the alternator and the starter post so I’ll take a look at that first, but I have a new alternator on my parts car as well.
  
  
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• #4 by ORCoaster on 26 Nov, 2017 10:38
• Sounds like a short shopping trip then.  More time to clean up the wiring between the alternator and battery.  Just remember no skinny wire for replacement, plenty of amps if working right.
• #5 by Rabbit79 on 26 Nov, 2017 15:11
• Best advice I can give is to check alternator output with a volt meter. Just put your meter leads on the battery terminals and with the alternator up and running and no lights or anything turned on they usually run in the 13.5 to 14.5 range. Rev the engine to see what happens when your RPMs go up. Also check the battery ground strap where it's attached to the transmission mount. Sometimes you can get corrosion down there which adds in some resistance and can cause all kinds of electrical mischief. I clean that area with a wire brush and then spray some of that battery corrosion preventive compound on it to seal it up.
• #6 by Tmarkle on 27 Nov, 2017 19:46
• Ok update... got the relay sound/lights dimming figured out, bad ground. So that’s solved. After I start it the lights are consistently dim till I really rev up the engine, then they brighten. The engine still wants to cut out sometimes but I’m working on finding anything else that could be. My battery tester says the the alternator is only putting out 35% of its potential, and the batter shows barely 12 volts when running.
  
  
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• #7 by ORCoaster on 27 Nov, 2017 20:25
• I have had this type of problem and I worked on it the following way. 
  
  1. Charge the battery to full with a battery charger from the house voltage.  Start with 10 amps and when full drop it down to 2 amp trickle charge and let it finish that cycle.
  2. Replace the voltage regulator if you have a Motorola style alternator it is a square box looking thing on the back.  Bosch are in with the brushes. It is tough to get a regulator to give us the 14.2 volts, most only provide 13.8 and that just doesn't cut it.
  3. Make sure the alternator belt is tight, diesel can make them stretch and you should have about 1/2 inch of deflection on the belt when you push on it between the pulleys.
  4. Put relays on the headlights and get the load off the headlight switch.  The switch should control only the relays and they will handle the higher current draw the lights demand. 
  
  I have an amp gauge in the car and it will jump up when I first warm the glow plugs but comes down to around 3-5 amps once they are off.  Charging at idle is pretty low amps, I don't generally see the alternator putting out 30 or 40 amps even though it is the 55 amp one.  Not sure what kind of draw would be needed to have that level of current generated.  Oh, big arse stereo system that's it. 
• #8 by Tmarkle on 09 Dec, 2017 16:53
• Is there supposed to be a wire attached to the W terminal? I know there was one attached to it on my Jetta but there isn’t on this rabbit. I’ve read that if the blue wire isn’t getting 12v then the alternator won’t charge either.
  
  
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• #9 by TylerDurden on 09 Dec, 2017 18:40
• The blue "exciter" wire is needed for the alternator to kick in... it also determines the state of the charging indicator. These machines usually need to rev >1000 to get the alternator started.
  
  The W terminal is for when any of tach/cruise/upshift_light/oil_pressure_alarm are present.
• #10 by rabbid79 on 09 Dec, 2017 18:51
• And make sure that exciter wire is also connected to a good load.  The load is usually the battery indicator light in the dash.  Make sure it's a good working incandescent bulb.  If you replace it with an LED, you're only asking for trouble.  An LED won't draw enough current, and you'll have to rev your engine really high to get the alternator to start outputting power.
• #11 by Tmarkle on 09 Dec, 2017 19:17
• If I really rev it up the lights really brighten up. There is no power to the blue exciter wire, so I think that’s my problem with the charging system.
  
  
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• #12 by TylerDurden on 10 Dec, 2017 14:49
• Easy way to tell if the exciter wire is bad (and they often are)... jumper a clip lead from the B+ (battery) wire to the D+ (exciter terminal). If the alternator immediately starts charging, the blue wire needs checking.
  
  LEDs have been used in the exciter circuit since the early eighties. They require just be bit more rev (~1000-1300rpm) to kick the alternator.
• #13 by rabbid79 on 10 Dec, 2017 18:48
• And that's exactly my point.  While it may be true that LEDs have been used since the early 80's, they cannot be used as a drop-in replacement in an application that used an incandescent.
  
  Unless you want and can remember to rev your cold motor up high enough to kick in the alternator.  If you forget, your battery will be exclusively supplying power until your alternator kicks in.
  
  If you're in the habit of letting your car idle in the driveway on snowing mornings with the fan on, lights on, heated seats on, and rear defroster on, this won't do good things for your battery.  You may come out and find your battery almost dead, all because you forgot to rev the motor, which you shouldn't do on a cold start anyway.
• #14 by Tmarkle on 10 Dec, 2017 19:58
• I will check out the blue wire and see if there is a break or something along those lines. I thought about converting it to a GM 1 wire alternator but I’d obviously rather just get the one on it working.
  
  
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