1G Crank No Start?

[Yamadaaaa009]

My car got flooded a bit. I was able to start it in neutral with no problems at first but the clutch and flywheel got stuck together (due to the water) so I was trying to start it in gear to free them up with no luck. After a few tries I tried to start it again in neutral and it cranks but doesn't start. Can't hear the fuel pump buzzing sound when you first start it so I'm guessing it's the fuel pump.

I was wondering where the fuel pump relay and fuse is? It's a 90 Eclipse N/T

Edit: forgot to add, we tried push starting and it still doesn't want to start

Thank you!

 

[steve]

We need to know if it's a 2.0L NA or a 1.8L NA. Assuming it's a 2.0L there are several resources here for you, some that are also useful for the 1.8L 4G37.

1G - 1G basic ECU MPI relay circuit function

The 1G DSM has two main circuits for the engine. The Multi Port Injection (MPI) circuit and the Ignition circuit. You must be registered to see element..The ECU is connected to both circuits but is powered from the MPI circuit and controls it. The MPI circuit also powers the MAF, CAS, ISC...

www.dsmtuners.com

1G DSM 1990-1991 Electrical Factory Service Manual

This is the 1990-1991 Mitsubishi Eclipse / Eagle Talon / Plymouth Laser Factory Service Manual covering:Electrical - Volume 2320 pages - 15MB -- use the link below to access.Here is the direct link from my Google Drive - You must be registered to see element.

www.dsmtuners.com

1G DSM 1990-1991 Engine, Chassis, Body Factory Service Manual

This is the 1990-1991 Mitsubishi Eclipse / Eagle Talon / Plymouth Laser Factory Service Manual covering:Engine Chassis Body, Volume 11216 pages - 70MB -- use the link below to access.Here is the You must be registered to see element. -You must be registered to see element.

www.dsmtuners.com

https://www.dsmtuners.com/threads/1990-engine-ecu-mpi-circuit-diagrams.540595/

1G DSM 1990 Technical Information Manual

Part of the promotional material from Chrysler previewing the then brand new vehicle

www.dsmtuners.com

The fuel pump relay is inside the MPI relay and uses the pink Ignition Fuse on the battery for it's power source.

Are you sure your battery is charged up?

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[Yamadaaaa009]

We need to know if it's a 2.0L NA or a 1.8L NA. Assuming it's a 2.0L there are several resources here for you, some that are also useful for the 1.8L 4G37.

1G - 1G basic ECU MPI relay circuit function

The 1G DSM has two main circuits for the engine. The Multi Port Injection (MPI) circuit and the Ignition circuit. You must be registered to see element..The ECU is connected to both circuits but is powered from the MPI circuit and controls it. The MPI circuit also powers the MAF, CAS, ISC...

www.dsmtuners.com

1G DSM 1990-1991 Electrical Factory Service Manual

This is the 1990-1991 Mitsubishi Eclipse / Eagle Talon / Plymouth Laser Factory Service Manual covering:Electrical - Volume 2320 pages - 15MB -- use the link below to access.Here is the direct link from my Google Drive - You must be registered to see element.

www.dsmtuners.com

1G DSM 1990-1991 Engine, Chassis, Body Factory Service Manual

This is the 1990-1991 Mitsubishi Eclipse / Eagle Talon / Plymouth Laser Factory Service Manual covering:Engine Chassis Body, Volume 11216 pages - 70MB -- use the link below to access.Here is the You must be registered to see element. -You must be registered to see element.

www.dsmtuners.com

https://www.dsmtuners.com/threads/1990-engine-ecu-mpi-circuit-diagrams.540595/

1G DSM 1990 Technical Information Manual

Part of the promotional material from Chrysler previewing the then brand new vehicle

www.dsmtuners.com

The fuel pump relay is inside the MPI relay and uses the pink Ignition Fuse on the battery for it's power source.

Are you sure your battery is charged up?

It is the 2.0L 4g63. The battery is charged up and we even tried to push start it with no luck but i will have to double check with a multimeter. Also I never really noticed before since I never had any problems with it but I assume I should be able to hear the stock fuel pump buzzing on the run key position right?

 

[steve]

Fuel pump only runs while your cranking or while the engine is rotating.

Since the starter will work independent of anything else, does the CEL turn on for 5 seconds when you turn the ignition on? If it doesn't the engine won't run.

 

[Yamadaaaa009]

Fuel pump only runs while your cranking or while the engine is rotating.

Since the starter will work independent of anything else, does the CEL turn on for 5 seconds when you turn the ignition on? If it doesn't the engine won't run.

CEL turns on. We added around 5L of gas cause we thought it just had no gas (fuel gauge is inaccurate) and it was able to run for like a second twice and it turned off immediately. Tried again and it's back to just cranking.

 

[steve]

That a step in the right direction. Have you inspected the ECU for capacitor leakage?
Damaged wiring for the Engine Coolant Sensor can cause starting issues and make sure that the ECU is activating (pulling it low) the second input to the Fuel Pump side of the MPI relay to keep the pump running.

 

[Yamadaaaa009]

That a step in the right direction. Have you inspected the ECU for capacitor leakage?
Damaged wiring for the Engine Coolant Sensor can cause starting issues and make sure that the ECU is activating (pulling it low) the second input to the Fuel Pump side of the MPI relay to keep the pump running.

Do I have to pull down and disconnect the ECU to check for those? I'm not familiar with what to check on the ECU yet so I guess I can just start by checking the wirings there. The ECU is behind the radio if I'm not mistaken?

 

[1990TSIAWDTALON]

It is and has 3 bolts holding it in. Steve is inquiring about the INSIDE of the ECU so you would need to remove the 4 screws that hold the cover on and look for things that look out of the ordinary. The capacitors are known to leak and cause damage to the ECU but it can usually be repaired. If you take your ECU out and take the cover off, take some pictures of the inside and post them for us to look at.
Marty

 

[Yamadaaaa009]

Ok, silly me thought that the oil light was the engine light. Upon checking I see no CEL light up while the ignition is on. That was my bad..
Also apologies for the dark pictures as I was only able to take it out at night but here's pictures of the ECU, I don't see anything blown or leaking but figured I should take some pictures.

EDIT: Just to add, I checked the pink fuse on the battery terminal (I think it's the MPI fuse) and switched it as well but no luck.

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[steve]

You can see that the capacitors were changed but the damage from the originals wasn't. The one closest to the connector is the main issue. I doubt the ISC was working very well when it was starting.

Unless you have another good ECU I'm once again going to refer you to https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-relay-circuit-function.435961/ so you can figure out if it's just damage to the circuit that activates the MPI relay or more extensive.

 

[Yamadaaaa009]

I'm guessing you mean these 2 were changed and the one in the bottom is probably the issue? Btw, is ISC = Idle Speed Control?
I currently don't have access to a VOM but I've got one coming, in the meantime I tried to check out the MPI relay and I can feel a click inside when I try to start the car. I'll come back again here once I've tried the debugging from your thread.

Thank you!

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[steve]

All three have been replaced but as you can see the circuit board is burned and the copper is corroded. In the center of that spot is what's called a via, a place where the circuit passed from one side to the other, and it's one of the 4 circuits to the Idle Speed Control motor.

 

[Yamadaaaa009]

Ok, I just did the MPI relay test and it seems to be good. Though I'm not that knowledgeable with it, I heard clicks on the tests and was able to get some voltage so I'm guessing the MPI Relay is good. I'm gonna have to send out my ECU to be checked but is there something else I can check before I send it out?

 

[steve]

Two things we are interested in; First is what happens when you ground pin 8 of the MPI relay. This is the pin the ECU used to turn on the power for the MPI circuit including the rest of the ECU. If the CEL then turns on and you can start the car you know that the problem is that the ECU isn't doing this. Second is that you have power to pin 103 on the ECU. This is the backup power used to retaining the memory of the ECU and to power the circuit that turns on the MPI relay. It comes from the 10A fuse #19 in the drivers side fuse box.

https://www.dsmtuners.com/threads/1990-engine-ecu-mpi-circuit-diagrams.540595/

 

[Yamadaaaa009]

Two things we are interested in; First is what happens when you ground pin 8 of the MPI relay. This is the pin the ECU used to turn on the power for the MPI circuit including the rest of the ECU. If the CEL then turns on and you can start the car you know that the problem is that the ECU isn't doing this. Second is that you have power to pin 103 on the ECU. This is the backup power used to retaining the memory of the ECU and to power the circuit that turns on the MPI relay. It comes from the 10A fuse #19 in the drivers side fuse box.

https://www.dsmtuners.com/threads/1990-engine-ecu-mpi-circuit-diagrams.540595/

This might sound like a stupid question but how do I ground pin 8 of the MPI relay? Do I do this while the MPI relay is in or do I pull out the relay first and ground the socket?

 

[steve]

A stripped wire inserted into the pin at the relay is how I do it. Everything needs to be connected for the test to tell us if that's the problem. Make sure you have the right pin, it's the one with the black wire with a blue stripe. There are lots of black wires with different stripes here.

Note: the diagrams show connectors looking into them. Here's a reference for where the pin is.

 

[Yamadaaaa009]

I grounded the mpi relay pin 8 and still no CEL... I guess that makes the mpi relay good? I also checked pin 103 in the ecu socket and had voltage.
I read somewhere to also check pin 110 while the ignition is on but I did not get any voltage there but I do get voltage from pin 108 when trying to start.

Also noticed that when I use pin 101 and 106 as ground I dont get readings on my multimeter, but I don't know how that works.

 

[steve]

No voltage to 102 and 107 means no power from the MPI relay. Make sure you have battery voltage at MPI pin 10, the big black/red wire. If you don't, the MPI fuse on the battery is blown.
Voltage to pin 103 means you have backup power to the ECU.
No voltage to 110 means the ignition switch isn't feeding power from the RUN/ACC position.
Voltage to 108 to during cranking means the ignition switch is feeding power while in the START position.

Pin 101 and 106 are best measured on a resistance scale with the ECU disconnected. You would measure the resistance between them and chassis ground and look for something very close to 0 ohms.

 

[Yamadaaaa009]

No voltage to 102 and 107 means no power from the MPI relay. Make sure you have battery voltage at MPI pin 10, the big black/red wire. If you don't the MPI fuse on the battery is blown.
Voltage to pin 103 means you have backup power to the ECU.
No voltage to 110 means the ignition switch isn't feeding power from the RUN/ACC position.
Voltage to 108 to during cranking means the ignition switch is feeding power while in the START position.

Pin 101 and 106 are best measured on a resistance scale with the ECU disconnected. You would measure the resistance between them and chassis ground and look for something very close to 0 ohms.

When checking pin 102 and 107 do I need to check it while cranking?

 

[steve]

When checking pin 102 and 107 do I need to check it while cranking?

No, those should have battery voltage on them right after you turn the ignition switch on. Those are the pins that get power from the MPI relay and are also connected to everything else on the MPI circuit. (MAF, CAS, ISC, Solenoids, Injectors, O2 Heater)

From your questions I'm assuming you can't read the wiring diagrams or follow what I wrote in the MPI article. That's OK but I need to know at what level to explain things.

 

[Yamadaaaa009]

No, those should have battery voltage on then right after you turn the ignition switch on. Those are the pins that get power from the MPI relay and are also connected to everything else on the MPI circuit. (MAF, CAS, ISC, Solenoids, Injectors, O2 Heater)

From your questions I'm assuming you can't read the wiring diagrams or follow what I wrote in the MPI article. That's OK but I need to know at what level to explain things.

Yes I cannot fully read wiring diagrams but I'm able to understand a few based on the information you've given. Unfortunately this is my first car that I'm working on and my background in cars are just simple maintenance, I do know a little bit but I'm afraid they're only surface level.

I just checked with the car again and here's a summary of what I can gather.
No voltage in ECU pin 102 and 107 but I think MPI Relay is good as I see voltage in pin 10 while ignition is on.
No voltage in pin 110 while ignition is on.
There's voltage to 108 while cranking.
ECU pin 103 also has voltage all the time.
Also I have no pin 101.... Is this normal? I dont see any wires hanging around the back that might be it and I've driven this car before so I'm guessing it is.

Could it be a wire issue from the relay to the ECU? From what I understand I should be getting voltage in 102, 107 and 110 while ignition is on. The wires were also still a bit wet due to the flooding and it's been constantly raining here. What got me thinking though is I was able to start it before and I did not see any problems, we're not sure how deep the water got in but it didn't seem to get into the ecu and only got into the seats and the flooring. It was running for a good 30 mins without any issues before I started to try to free the clutch from the flywheel by trying to start in gear a lot of times.

 

[steve]

I just checked with the car again and here's a summary of what I can gather.
No voltage in ECU pin 102 and 107 but I think MPI Relay is good as I see voltage in pin 10 while ignition is on.
No voltage in pin 110 while ignition is on.
There's voltage to 108 while cranking.
ECU pin 103 also has voltage all the time.
Also I have no pin 101.... Is this normal? I dont see any wires hanging around the back that might be it and I've driven this car before so I'm guessing it is.

Could it be a wire issue from the relay to the ECU? From what I understand I should be getting voltage in 102, 107 and 110 while ignition is on. The wires were also still a bit wet due to the flooding and it's been constantly raining here. What got me thinking though is I was able to start it before and I did not see any problems, we're not sure how deep the water got in but it didn't seem to get into the ecu and only got into the seats and the flooring. It was running for a good 30 mins without any issues before I started to try to free the clutch from the flywheel by trying to start in gear a lot of times.

Lets look at this again.

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Power from the the MPI fuse on the battery to pin 10 on the MPI relay. It's unswitched so you should always have battery voltage present at pin 10.

Pins 4 and 5 on the MPI relay are the switched outputs of the relay. They connect to ECU pins 102 and 107. (You can't see 102 on this diagram).

ECU Pin 110 (thick Black/White wire not show here) comes from the ignition switch. It should have power whenever the ignition switch is in the ACC, RUN, or START positions (what's called IG1). This pin, when it has battery voltage on it, tells the ECU to turn on (and off later when it goes to ground). Assuming your looking at the correct pin that fact you don't indicates a problem before the ECU. The ECU then pulls pin 63 to ground turning on the MPI relay which provides power to the rest of the ECU and a large part of the engine bay.

ECU Pin 108 also comes from the ignition switch but this one only has power then the ignition switch is in the START position. This signal tells the ECU to prepare to start and also causes the fuel pump to run by providing battery voltage to MPI relay pin 9 which flows through the coil in the relay and out pin 6 to ground. That activates one of the two fuel pump coils in the MPI relay.

As mentioned in an earlier post ECU pin 103 is the backup power for the ECU. It is unswitched and comes from the 10A fuse #19 and should have power all the time.

ECU Pin 101 may not be present on a N/T car. It's a ground and connected to pin 106, so if one or the other is connected it works.

I suggested you ground MPI Relay pin 8. You'll note, it's connected to ECU pins 63 and 66. It normally has battery voltage on it since it's connected to MPI Relay pin 10 via a diode and a relay coil. When you or the ECU grounds it the relay should activate and power is switched from MPI Relay pin 10 to MPI Relay pins 4 and 5. It wasn't clear if this happened when you tried, since I went directly to have you check for ECU signs of life (the CEL). If it does but the ECU doesn't turn on, you have an ECU problem.

Since you don't have battery voltage on ECU pin 110 when the ignition is on but you do get battery voltage on ECU pin 108 when the switch is in the START position it would seem like you have a bad switch or wiring issue.

When you look at the diagram above you see that diagram tells you which connector, where the pin is, and the color of the wire to that pin. In the manual the colors are spelled out as (marking color is the stripe):

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The view of the connectors is looking at them from the back where the wire poke out which is also how you would see the connectors that they plug into. I go into more detail in https://www.dsmtuners.com/threads/how-to-identify-ecu-pin-numbers.246467/

 

[1990TSIAWDTALON]

Thanks @steve for all of the help that you give us ALL! This forum wouldn't be the same without you!

 

[Yamadaaaa009]

Thought I had updated this thread but I guess not. Might help some people. I've had the ECU caps replaced but still didn't had any CEL. I double checked the MPI relay following the manual again and it all seems good but then I got curious and opened the relay up, to my surprise it's all rusted out inside and seems like water did get inside. I've rewired to use 4pin relays in the meantime, now it's been around 5 months and it's running again, it's a temporary fix but I saw an article on this forum regarding this so this should last a long time. I still plan to buy a working mpi relay but now I can work on other problems