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Car Forum / Mitsubishi Cars / April 20061992 mitsubishi expo 1.8 L no spark
I have a 92 mitsubishi expo 1.8L LVR with 200,000 miles last week it just stalled when going around the corner. No spark, removed the ejector line and all 4 ejectors fired and sprayed fuel. I'm looking at replacing the dist. but whould like to know how to test it before I buy one. I was told to check for a 5 volt signal on the input to the dist. which come from the ECU. I was told it fires the bipolar transistor in the dist assy. I don't want to find out that the problem was the ECU or even maybe the timing jumping a tooth. does this make sense? Thanks Mario > I have a 92 mitsubishi expo 1.8L LVR with 200,000 > miles last week it just stalled when going around the corner. No spark, [quoted text clipped - 6 lines] > > Thanks Mario Did you check the ECU diagnostic output pin for an error code. All you need is a jumper wire and an analogue meter. This vintage ECU is prone to failure, (but is also easy and cheap to fix). When was your timing belt last changed / checked. And because you asked, Pin 6 on the dist plug should have an active ground to fire the coil. Normally there is a pulse train at this point, supplied by the ECU, if and when other sensors tell the ECU when the crank position is correct to fire a SP. When pin 6 is grounded, pin two will swing from 12 volts to ground (if the transistor is working) and the coil should fire. Note that the ignition switch needs to be in the "run" position for this to happen. The manual suggest the following procedure to test the transistor. 1. attach a 1.5 volt battery (negative side) to terminal 5 of the connector block. Connect the positive to terminal 6 of the connector block, intermittently, while measuring the resistance between pins 6 of the 6 pin connector block, and pin 2 of the two pin connector block (negative meter lead to pin 2). 2. Battery connected, very low resistance 3 Battery disconnected, very high resistance. Pin 6 should be Green-Yellow Pin 5 should be Black Pin 2, on 2 pin connector block, should be White-Black O BTW, the primary of the coil is across pins 1 and 2 of the two pin connector, the secondary is across pin one and the rotor. But first thing I'd do is check the ECU trouble code. If the signal is constantly high, the ECU is toast. If the signal is constantly low, the ECU has no power, If the signal is a 50% pulse train, the ECU is working fine. Any other pulses are actual error codes. All this is based on a 1992 Mitsubishi 1.8 liter eclipse, but it should be the same. If you don't have an analogue meter (that's a meter with a dial), buy one, a cheap one (under $10.00 CDN) will do just fine for these tests. All you need is one that can measure a voltage of 20 volts or less and a resistance up to 20,000 ohms. Hi First, I want to thank you, so so much for taking the time to explain and answer my question. I’m buying a Mitsubishi factory service manual but, I won’t have it for a week or so. This will give me a good point to start at. I’m a little confused on the ECU diagnostic pin. I don’t know where to find it. I do have a Simpson 260 meter & O-scope. Is this a point on the ECU where you can verify the pulse train and determine that the module is working properly? I have read where replacing both the dist & ECU did not resolve the problem. I think this was due to the timing belt jumping a tooth. I’m not sure if this applies to my situation. My belt was replaced back at about 115,000 mile, so it may be due. Maybe, the best thing is to do all three. Normally, I won’t waste time on a car with this much mileage, but it was such a good running car. I miss not having it. Thanks again for your help Mario > Hi > First, I want to thank you, so so much for taking the time to explain and [quoted text clipped - 16 lines] > > Mario On an eclipse, the diagnostic plug is located on the right side of the fuse panel, which is against the left wall of the passenger compartment, under the dash. It's a 12 pin connector, with nothing attached to it. Usually covered by a plastic dust cover. Pin one outputs a pulse (attach the positive of the meter here), depending on the error code or status of the ECU (vehicle ignition needs to be in the "run or ON" position). Pin 12 is a ground point (attach the negative of the meter here). However, you may not need the ground on pin 12 to enable the ECU output. Attaching the negative lead from you meter to a good ground should be OK. Attach the meter with alligator clips, then turn the car to the "run" position. Watch the needle deflections, that's the code output. Longer pauses, indicate the space between digits of the error code. Example; two long pulses, one longer pulse, then three short pulses, (signals then repeats) is code 23 on an eclipse, which is "number 1 cylinder, top dead center sensor" , output error (on a 1991 Eclipse), yours may be different. Your service manual will have all the codes. With your meter and O-scope, you should be able to test every electronic item in your car, including all the engine management sensors. If the ECU is toast, let us know, don't replace it. There is a web page that has all the details on how to repair it, for about $5.00 CDN in parts. If you have 85,000 miles on the timing belt I would suggest you replace it now, as well as the balance shaft belt, tension pulleys, and water pump ( I guess it depends on how long you want to keep the car, hows the compression on the engine). Remember, these details apply to an Eclipse, of your vintage, your car may be slightly different. Hi Again Yes,I did see that connector. And now,it all makes sense. Is the fix for the ECU the replacement of the 3 electrolytic caps? That would be way to easy.... From what I'm reading, it appears that this Mitsubishi ECU was one of the most likly to fail. I was getting unexplained bucking every now and then. I just thought it was a bad fuel ejector. Would that be the processor doing a reset because of the caps? I took a quick look at mine and they all look good, maybe I should replace them. So,I now think I can test both the Dist & Ecu. Your information has been very helpful. My bet is now on the ECU and not the Dist. I'll let you know Thanks Mario > Hi Again > [quoted text clipped - 13 lines] > > Thanks Mario That is the usual fix. I would do the ECU capacitors on spec. But first check the diagnostic output codes. Pay close attention to the larger capacitor right in the middle of the circuit board. Usually there is some material, like contact cement, used to hold it a bit better to the PCB. On two of the ECU's I've worked on, under that material, there has been a break on the thick trace on the PCB. Almost looked like it was on purpose, as the gap was about 1/2 mm wide. Using your scope, you can also check the TDC sensor, pin 4 (Blue wire) of the 6 pin block and the crank angle sensor, pin 3 (brown-yellow wire) of the same connector. Should see a 5 volt pulse train as the engine cranks. On my Eclipse, they are both located in the dist. OBTW, the capacitors are an industry wide problem. I've even replaced them on a year 2000, IBM Aptiva system board, as well as switch mode power supplies. Good luck Ray Hi Ray I need your help once again. On the 12 pin connector, there are only seven wires connected. I take it that pin 1 is yellow/red (pulse train) pin 12 grn/blk (Ground). Second: question, you mention that there is a 1/2mm gap, is that for the cap spacing ? Or a problem that needs to be addressed. Third: I noticed on the pc(ECU)board that there are 4 transistor drivers, are they for the fuel ejectors, and the one transistor driver in the middle for the Dist driver to excite the coil. That's just an observation on my part. My last question. I remember reading in a post, that if the timing belt jumps the ECU will know and halt the pulse to fire the coil. This may be a form of protection for the valve and piston clearance.I'm not sure if this is true for this vintage Mits. Thanks once again, I can't thank you enough for all your help Mario P.S. I'm still waiting for my factory service manual. > Hi Ray > [quoted text clipped - 20 lines] > > P.S. I'm still waiting for my factory service manual. My eclipse manual (Laser manual) shows pin 1 as yellow, pin 10 as white,pin 11 as yellow-white, pin 12 as black The row of pins that includes the "key" (two missing pin positions) is the low count pins ( 1 to 6) Pin one is on the side that has three pins. Pin one is closest to the edge. The 1/2mm gap was in the actual copper, circuit trace. Almost like somebody cut part way threw the trace, maybe making it a safety blow out fuse. Don't know for sure about the transistor drivers. Injectors are wired to pins 51, 52, 60, and 61 of the ECU pins. Pin 62 controls the purge control solenoid. Pin 54 is the drive for the power transistor in the dist. When I installed the timing belt on my sons Laser (Eclipse, sort of) I was one tooth out. The car ran fine (but gutless), till you got to a hill then it hardly moved. Can't answer for sure about your last question, but my guess is it's not smart enough to know if the belt jumps a few teeth, but it would not see and pulses for the TIC and crank angle sensor in the dist if the belt is totally broken. Ray Hi Ray I see there is a difference on the color code. So'I look over the Net and I see over and over again that the caps seem to be the problem. Since I can't wait any longer for this service manual, I decided to check the caps, and guess what,the 100 uf is shorted. So tomorrow, at work I will bring it to our electronics lab and desolder all three caps. I hope I did cause any problems on my dist. I started to remove some of the parts to check the coil. I need to get a new gasket for the cover. I hope this will solve the problem, because right now both of my cars are broken. I see that you have help quit a few people with this problem. How did that women make out with her car? Looks like she got 4 ECU at a junk yard and all four were bad, but at 50 cents each I guess she got a good deal. Thanks again Mario > Hi Ray > [quoted text clipped - 19 lines] > > Mario Not everybody gives feedback of a successful repair. You never did tell me what you found on the diagnostic output lead. To test all aspects of the dist., you did not have to take it out of the car. It's keyed, so you can only install it in one direction. I'll be off the air for a while, it's summer. Good luck with your cap repair, I guess you know you can use larger value caps, if you want. Ray > Hi Ray > [quoted text clipped - 19 lines] > > Mario OK, I'm back, Maui was nice, almost didn't come back. How did you make out with the ECU, and your vehicle. Ray Hi Ray All the factory manuals came in today. I replaced the caps and then retired but no luck. The caps were not shorted at all. I was reading the wrong points. They really looked good, but I replace them always. I found the data out which is pins 112 & 113 on the ECU. The funny part is I'm get 5 long pulses and 5 short pulses I check and rechecked the only thing I can see is maybe its a 44 trouble code which is a bad ignition coil or power transistor. However the manuals says that for the 2.0L not 1.8L I check the Dist now that I have the schematics of the wiring diagrams. The power transistor a NPN the pins are: pin 5 emitter pin 6 base and pin 12 (on the Tach) the collector. The manual says you should get 3 volts to fire the base to emitter 'm getting 1.75 volts. Here is the part that looks wrong. The base to collector has resistance in one direction, less than 300 ohms very high in the other direction.I seem to remember that this should be high in both directions. The emitter base ratio is less than 10. (30 ohms foward biased) (150 ohms reverse biased)I still hate to replace it cause I read where another person had a problem where he said the transistor failed the test (low volts) but found the caps to be the problem. Maybe I should read all the voltages on the ECU ?????? What your thoughts Mario I did find a fault code 55 for the 1.8 L model. It is known as IAC Idle air control valve sensor. I sure this has no effect on my ignition problem. It may however prove that the ECU is working maybe?????? > I did find a fault code 55 for the 1.8 L > model. It is known as IAC Idle air control valve > sensor. I sure this has no effect on my ignition problem. It may however > prove that the ECU is working maybe?????? If your getting error code 55, then your ECU is running. Don't rule out the IAC sensor, until after you have tested it. Pin numbers almost match, I have base on pin 6 emitter on pin 5 and collector on pin 2, tach feed. Are you sure you ment pin 12, or might it be a typo. Think of the power transistor as two diodes, with a common point (the base). Base/emitter and Base/collector. IN both cases, you should get a high resistance in one direction (base/emitter for example) and a low resistance in the other direction (emitter/base). Remember that there may be other components in the circuit, which could give you a false reading (a tach for example). It's best to use the test in the service manual, as it actually tries to operate the transistor. You need a 1.5 VDC battery to simulate the pulse train from the ECU. The procedure is in the "Ignition system - Distributor" section.. Remember that if you fire the transistor (Ignition in run position) you should get a spark on one of the plugs. With the ignition switch in "run" position, you should see 12 volts at the tach connector (pin 12 for you, pin 2 for me). When the transistor fires, you should see a ground at this point. The transistor switches a ground onto the coil to charge it, then removes the ground to fire it. You can simulate this by applying a ground, very temporairly, to (pin 2 for me, pin 12 for you), while holding a grounded screw driver next to the center pin of the distributor (pull the cap off). Ignition switch in "run" position. If the coil is good you should get a good spark. As well, you can measure the resistance of both sides of the coil, the values are in the service manual. Actually on this dist, you should be able to test everything. Ray Hi Ray I did the battery biasing test from the manual. They said to hook the battery +1.5 volts to pin 6 base and -1.5 volts to pin 5 the emitter which is grounded when connected to the dist. Then take the ohm meter and connect the neg probe to pin 12 the tach(collector) and the pos probe to pin 5 the emitter. This was done with both connectors removed from the dist. It failed because it had continuity with or without the battery connected. From the diagrams of the manual I can not see any other path to addd to the low resistance reading. Again looking at the diagrams with the CONNECTORS OFF I only see the the power transistor in series with the primary dist. coil. I tried the temperary grounding of the tach wire pin 12 (collector)with connectors on. This of course is bypassing the transistor totally. I did not get any spark from the secondary of the coil. This may be due to the low resistance from the collector to emitter. I think it's time to replace the dist. I don't know of any other testing I can do. Thanks Mario > Hi Ray > [quoted text clipped - 18 lines] > Thanks > Mario OK, one last test. Disconnect pin 5 from the multi position connector. This is the pin connected to the emitter of the power transistor. It provides the ground for the coil, when the transistor triggers. Disconnect pin 6 from the multi position connector. This is the pin connected to the base of the transistor. Now momentarily ground the tach lead (pin2 for me, pin 12 for you). Monitor the secondary output, if all is well you should get a spark. This bypasses the transistor, and takes it out of the circuit. Remember that the ignition should be in the "run" position, and just to make sure, measure the primary coil side for 12 VDC at pin 1 (on my diagram the lead is called "Ignition switch 1G1"). If the tach side isn't grounded, you should also see very close to 12VDC. Here's another way to do the same thing. Disconnect both connectors from the dist. Apply 12VDC to the primary side of the coil (pin 1, the one that is common to both the primary and secondary coils). Ground pin 2 (pin 12), the tach lead, momentarily. The secondary should spark (center point of dist, cap removed). Here's a rambling thought. If the transistor is indeed gone, you could attach an external one, by connecting the collector to pin 2 (12), the base to pin 6, and then grounding the emitter. Of course you'd want to disconnect pins 5 and 6 from the dist. Please be aware that semiconductor representations on these service manuals, are just that, representations of real circuits, and do not represent actual electronic wiring. That power transistor could be a Darlington, for example. Good luck. Ray Hi Ray Today was a great day.. First thanks again so much for helping. I hope I can return the favor someday.. After doing that test I decided if was time to replace the Dist. So I took my Simpson, and went to the junk yard and purchased a dist. When I when to test it before buying it, I end up getting the exact same readings on the replacement. So now I not sure what to do. The guy said he took it from a running 93 Expo. Well, for $65.00 I took the chance. I didn't feel very good about because I didn't think it would work. The screw on the dist cap was broken. I had to retap to get it secure. So I came home, took a few hours break, and then I replaced it, and guess what, I worked.....So here is my conclusion. It wasn't the so called transistor and it was not the coil. What I think the problem was in the camshaft or crankshaft sensor. Thats the only part of the dist I didn't check. The manual is misleading you have resistance from the emitter to collector pin5 to pin12. This test makes you think the transistor is bad, but infact it good. They speak of continuity and no continuity. They should say what the resistance values are. So to any reading this, I hope it helps you solve your problem. The garage wanted $350.00 plus labor for a rebuild. I was vey close to doing it but decided to check this board. And thanks to Ray who took his time to help I was able to get the fix with out spending hundreds of dollars. I'm enclosing my e-mail incase I'm not reading this board. marios2468@aol.com please feel free to ask any questions I have the complete factory manual from Mitsubishi. Mario >If the ECU is toast, let us know, don't replace it. There is a web page >that has all the details on how to repair it, for about $5.00 CDN in parts. Hi What Is The WebSite So I Can Fit My Ecu Thanks |
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