 Trouble shooting the Fuel Injection, Checking the volts and resistance on a D-Jet 1.7 '70 |
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| tabs914 |
 Oct 16 2009, 01:58 PM
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#1
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Advertise Your Drive...  Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None  |
Hello all... I have been trying to trouble shoot my non-starting 914(just cranks). I figured I would start on the fuel injection system, making sure the ECU is getting the proper signals. Here is what I have checked:
MPS Vacuum: Holds 5 Min. + Main Coil: 56 ohms SPEC: 90 Secondary Coil: 348 ohms SPEC: 350 Injectors: SPEC 3 ohms for all injectors Inj 1: 3 ohms Inj 2: 3 ohms Inj 3: 2 ohms Inj 4: 2 ohms Throttle Position Switch Idle Contact: Spec .5 ohms .68 ohms Head Temp Sensor: SPEC 2k ohms Also it is new... 3k ohms I cleaned the trigger points (I don't know if it was a fluke, but this sparked a stummble for one second, only once) New cap/rotor/points Checked Spark from coil wire (Good) Checked Spark from cap (good) Checked Spark at plug (good) Fuel Pump Primes when key is turned Checked the injectors for pulse (when cranking) Good. New fuel filter and lines (the pump is installed correctly I have checked several times (IMG:style_emoticons/default/smile.gif) The AAR warms up if connected to 12 volt. warm closes and opens when cooled down. (not sure if it should do this if I just turn the ignition on? - doesnt seem to warm up if I do.) New vacuum lines backed up with clamps on all connections I can't check fuel pressure - I don't have a guage nor for compression either. Anyone in Portland, Oregon or Vancouver, Washington I can borrow from? (IMG:style_emoticons/default/smile.gif) Maybe someone in the area that can help me out, would be very cool. I am learning alot, but this has me stumped. I haven't had her on the road yet, but I had this baby running pretty well. I was messing around with the head temp sensor when it died. I thought maybe the wire lead became damaged within the sensor casing? Bought a new sensor with no effect. I have three ECU's and I know two work (no effect) The triggers seemed to sparked a stumble, they look ok... any way to test them? Thank you for your help. (IMG:style_emoticons/default/biggrin.gif) Tab |
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| type47 |
Oct 16 2009, 03:15 PM
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#2
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
Trigger points are just basically on-off switches, little to no adjustment. You can make a fuel pressure gauge with a gauge from the plumbing dept of Home Depot or Lowes or whatever your hardware store is. Get the barbed fitting and whateverelse is needed to screw the gauge into and a piece of FI hose and you're good. But, if it was running good before, I doubt the pressure changed. Definately need the head temp sensor to start though, needs to be ~3k ohms cold decreasing to low resistance (single digit ohms?) when hot
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| underthetire |
Oct 16 2009, 03:22 PM
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#3
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
Harbor freight sells a fuel pressure tester. It's usually on sale for 7 bucks or so. Has the barbed fitting and a bunch of other adapters. Good home garage tool. Hell, you can barely make one from hardware store parts for that.
http://www.harborfreight.com/cpi/ctaf/disp...temnumber=92699 Guess it's not on sale this week, it usually is, but here is a coupon for 15%off. http://www.harborfreightusa.com/usa/common...mp;keycode=0000 |
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| tabs914 |
Oct 16 2009, 03:24 PM
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#4
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
QUOTE(type47 @ Oct 16 2009, 02:15 PM)  Trigger points are just basically on-off switches, little to no adjustment. You can make a fuel pressure gauge with a gauge from the plumbing dept of Home Depot or Lowes or whatever your hardware store is. Get the barbed fitting and whateverelse is needed to screw the gauge into and a piece of FI hose and you're good. But, if it was running good before, I doubt the pressure changed. Definately need the head temp sensor to start though, needs to be ~3k ohms cold decreasing to low resistance (single digit ohms?) when hot 3k at the sensor or at the ECU? Thanks (IMG:style_emoticons/default/biggrin.gif) |
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| tabs914 |
Oct 16 2009, 03:25 PM
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#5
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
QUOTE(underthetire @ Oct 16 2009, 02:22 PM) Harbor freight sells a fuel pressure tester. It's usually on sale for 7 bucks or so. Has the barbed fitting and a bunch of other adapters. Good home garage tool. Hell, you can barely make one from hardware store parts for that. http://www.harborfreight.com/cpi/ctaf/disp...temnumber=92699 Guess it's not on sale this week, it usually is, but here is a coupon for 15%off. http://www.harborfreightusa.com/usa/common...mp;keycode=0000 Thats cool... thank you!!! |
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| aircooledtechguy |
Oct 16 2009, 03:35 PM
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#6
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The Aircooledtech Guy Group: Members Posts: 1,966 Joined: 8-November 08 From: Anacortes, WA Member No.: 9,730 Region Association: Pacific Northwest |
QUOTE(tabs914 @ Oct 16 2009, 02:24 PM) 3k at the sensor or at the ECU? Disconnect the sensor from the ECU and test the sensor by itself. Positive test lead in teh spade, negative test lead to the base of the sensor. You may also test the difference to the head where it screws into. If there is a big difference, you have corrosion in the threads (I've seen this once). These keep the motor from running and can strand you if they go bad. I recommend my clients carry a spare (since they are so cheap). |
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| tabs914 |
Oct 16 2009, 03:58 PM
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#7
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
QUOTE(aircooledtechguy @ Oct 16 2009, 02:35 PM) QUOTE(tabs914 @ Oct 16 2009, 02:24 PM) 3k at the sensor or at the ECU? Disconnect the sensor from the ECU and test the sensor by itself. Positive test lead in teh spade, negative test lead to the base of the sensor. You may also test the difference to the head where it screws into. If there is a big difference, you have corrosion in the threads (I've seen this once). These keep the motor from running and can strand you if they go bad. I recommend my clients carry a spare (since they are so cheap). What should the reading be? (round about?) |
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| type47 |
Oct 17 2009, 08:27 AM
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#8
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
2-3k ohms according to:
http://www.914world.com/bbs2/index.php?sho...CHT++resistance as directed above, you disconnect the CHT sensor from the harness; you don't want to see resistance from the ECU. 'course, what has not been discussed so far is replacing the CHT (IMG:style_emoticons/default/biggrin.gif) Disconnect the CHT at the sensor and measuring resistance takes like 2 minutes. |
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| JFJ914 |
Oct 17 2009, 08:44 AM
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#9
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Senior Member Group: Benefactors Posts: 813 Joined: 13-June 03 From: Alpharetta, GA Member No.: 814 Region Association: South East States 
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The D-Jet "Bible" http://members.rennlist.com/pbanders/ . Go here and all will be explained
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| BMXerror |
Oct 17 2009, 10:06 AM
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#10
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Senior Member Group: Members Posts: 1,705 Joined: 8-April 06 From: Hesperia Ca Member No.: 5,842 |
This may be way basic considering tests that you've already done, but an engine needs four things to run; air, fuel, spark, and timing. It sounds to me like you've got the first three covered. I would recommend taking some time to double check your connections and base settings. Make sure your plug wires are in the right place. Set the 'bench timing' on the ignition (lemme know if you don't know how, and I'll tell you). Also, make sure that your point gap is set right.
Just some things to think about. And it's not a commentary on your skills, because I've done all the same things. (IMG:style_emoticons/default/biggrin.gif) Mark D. |
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| sean_v8_914 |
Oct 17 2009, 10:29 AM
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#11
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Chingon 601 Group: Members Posts: 4,011 Joined: 1-February 05 From: San Diego Member No.: 3,541 |
...did you check for spark at a plug?
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| swl |
Oct 17 2009, 11:55 AM
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#12
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Senior Member Group: Members Posts: 1,409 Joined: 7-August 05 From: Kingston,On,Canada Member No.: 4,550 Region Association: Canada |
QUOTE(John Jentz @ Oct 17 2009, 06:44 AM) (IMG:style_emoticons/default/agree.gif) Check for your resistance and grounds from the harness where it connects to the ecu. 'be the ECU' (IMG:style_emoticons/default/smile.gif) That way you can check the harness as well as the component. Given you went from great to nada while doing some work I would suspect the harness. |
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| tabs914 |
Oct 17 2009, 12:07 PM
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#13
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
Thank you all for your suggestions... I really appreciate it. (IMG:style_emoticons/default/biggrin.gif) Well going to the store and buying some more testing equipment has narrowed my search for the culprit...
I tested the compression. I could only do this on a cold motor of course, but here are the results: 1: 145 2: 148 3: 148 4: 145 ...looks like fuel. I hooked the fuel pressure gauge to the test port... turned the key and heard the pump prime then continued to crank the motor for 8 seconds or so... zero on the gauge. Second attempt same thing. I pulled the gauge and it was dry. It doesn't look like there is a valve on the port so it appears that there is a supply issue... and yes I have a 1/4 tank of fuel. (IMG:style_emoticons/default/lol-2.gif) more things I can try? |
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| swl |
Oct 17 2009, 12:13 PM
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#14
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Senior Member Group: Members Posts: 1,409 Joined: 7-August 05 From: Kingston,On,Canada Member No.: 4,550 Region Association: Canada |
sounds strange. if you hear the pump it should be moving fuel.
Have you done any work on the fuel lines? |
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| swl |
Oct 17 2009, 12:23 PM
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#15
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Senior Member Group: Members Posts: 1,409 Joined: 7-August 05 From: Kingston,On,Canada Member No.: 4,550 Region Association: Canada |
one thought...
The three port pumps have a fail mode where they wind up pumping through the return port rather than the delivery port. Way too much of a coincidence for that to happen when you are working on electrical stuff but i guess stranger things could happen. Do you hear any gurgling in the tank when you turn the key on without starting the car. The pump runs for a second or two with key on. Do that a couple of times and you should hear the return being dumped back in the tank. |
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| tabs914 |
Oct 17 2009, 12:29 PM
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#16
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
QUOTE(swl @ Oct 17 2009, 11:13 AM) sounds strange. if you hear the pump it should be moving fuel. Have you done any work on the fuel lines? I started this thread because originally this car hadn't ran for 20+ years and I decided to ditch the old motor... (water, rust, etc.) so here is a link to post #78 of that thread showing some of the things I have done to this point. http://www.914world.com/bbs2/index.php?s=&...t&p=1219512 I have touched/changed and refreshed allot of things. Do you think that the HT sensor could short the fuel pump or send a false signal to the ECU to not fire up the pump? (IMG:style_emoticons/default/confused24.gif) |
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| tabs914 |
Oct 17 2009, 12:30 PM
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#17
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
QUOTE(swl @ Oct 17 2009, 11:23 AM) one thought... The three port pumps have a fail mode where they wind up pumping through the return port rather than the delivery port. Way too much of a coincidence for that to happen when you are working on electrical stuff but i guess stranger things could happen. Do you hear any gurgling in the tank when you turn the key on without starting the car. The pump runs for a second or two with key on. Do that a couple of times and you should hear the return being dumped back in the tank. I will go check... thank you. |
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| tabs914 |
Oct 17 2009, 01:36 PM
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#18
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Advertise Your Drive... Group: Members Posts: 105 Joined: 17-January 05 From: Gresham, Oregon Member No.: 3,456 Region Association: None |
I can't hear any gurgling...
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| Jacob |
Oct 17 2009, 01:51 PM
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#19
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Member Group: Members Posts: 131 Joined: 12-February 08 From: Mansfield, Oh Member No.: 8,705 Region Association: Upper MidWest |
Can you pull the lines leading into and out of the fuel pump? I think the the fuel pump just runs for four seconds regardless of whether or not you have pressure. It would be nice to see if fuel is even getting to the pump. Might be a plugged line.
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| tod914 |
Oct 17 2009, 02:07 PM
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#20
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Advanced Member Group: Members Posts: 3,755 Joined: 19-January 03 From: Lincoln Park, NJ Member No.: 170 |
You should be able to peek in the tank with a light and see if the filter sock is clogged. The AAR works off of the same fuse as the pump. But, it would more than likely blow the fuse if it was shorting out. Couldn't hurt to unplug the AAR to test. Sound like a clog or misrouteing. You mentioned in the other thread the fuel system was removed. You can try swapping the lines inside the engine bay by the battery tray where they attach to the plastic lines (feed and return). If they are swapped, you will not get pressure. Pelican has a fuel routing diagram too if you need it.
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