Intermittent start no start issue?

Hi,

Did you jump pins 30 and 87 at the fuel pump relay? Those are the ones to power the pump. Also, pin 85 is a ground part via the PCM. So, it shouldn't have power. However, it should provide a ground when the key is turned and in the run position. Have you checked for that?

Next, if you checked for power with the relay removed, you should only have power to pins 30 and 86. Is that the case? Note: Pin 30 should have battery voltage at all times. Pin 86 only has power when the key is in the run or start position.

Take a look at this link, you may find it helpful:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know.

Joe

See pic below.

Hi,

I doubt the PCM or Crankshaft position sensor is faulty. Also, I didn't realize there was a no-bus signal on the dash.

The PCI Bus failure modes are broken down into two categories, complete PCI Bus Communication Failure and individual module no response. Have you tried scanning the CAN to determine if there are specific codes that are stored for a specific module?

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Also, I attached the wiring schematics for the entire powertrain management circuits. I highlighted all wires related to the fuel pump.

Confirm power is present to the two pins (30 and 86). Pin 30 should have constant power and 86 should have power with the key in the run position.

If that is present, check connector pin 85 for a ground signal when the key is in the start position. To do this, attach the alligator clip end of a test lamp to the battery positive. Probe the opposite end in pin 85. Have a helper turn the key to the on position. The test lamp will turn on if there is a ground path.

Let me know.

Joe

See pics below. Note: The schematic was four pages long. I had to cut each in half to make them readable.

Hi,

If you are unable to connect with a scanner, have you checked if pin 16 gets power at the DLC? It should have a constant B+ voltage and be powered by fuse 1 in the under-dash junction box. Also, pins 4 and 5 should be a ground on the DLC.

I attached the wiring schematic below for the can circuit. The next to the last circuit on the left is the PCM signal. If there is a communication error (bus) that is the area I would start checking. I highlighted in the last pic below a joint connection between the DLC and the PCM. If you disconnect the PCM, check to see if there is continuity in the pink wire between the two.

Let me know.

Joe

See pics below.

Hi,

The code is related to the fuel pump relay circuit. I attached the diagnostics below specific to your vehicle and the code.

I have a question. If you feel the relay click, that tells me the primary side is working. If you are not getting power to the pump, there is likely an open between the two. If there is power, the pump may be faulty. However, the pump shouldn't cause this code.

Let me know.

Joe

See pics below.

As far as the pump, are you sure by accident you didn't switch the supply and return lines? I've seen it happen before.

As far as the PCM, I'm not sure what to tell you. If you were able to get the VIN programmed, it should work. The fuel pump, on the other hand, will automatically shut down after the prime. For it to turn back on and run constantly, you need to have ignition. Are you certain there is spark to the plugs?

Let me know.

Joe

Hi guys. I stumbled across this and have been waiting to learn the solution. I'd like to add a comment of value in case it helps.

I had the gas tank out of my '88 Grand Caravan twice to replace a plugged strainer, and both times, being the expert I think I am, I switched the fuel supply and return hoses. They're different sizes, yet I was able to mix them up.

More importantly, since your tank was out, I suspect you pumped the gas out. Inside the tank, the fuel pump housing and strainer sit inside a bowl that prevents the gas from running away from the pickup when you go around a corner or uphill when the fuel level is low. That bowl is kept full by the fuel coming back on the return line. When you start out with an empty tank and add gas, it dumps right into that bowl. All I needed to get my engine started was a pint of gas.

On my '94 Grand Voyager, they use a similar setup, except when you put gas in, it misses that bowl. I found when parked on level ground, I needed to put in close to five gallons before it would get high enough to spill over into the bowl. Once that happened, the pump could draw fuel, the engine would run normally, and the returning gas kept the bowl full, as usual. At that point you could use up the entire five gallons. The point of my sad story is you might have to put more gas in the tank to get fuel pressure up for the first time.

As Joe mentioned, the fuel pump only runs for one or two seconds when the ignition switch is turned on. That's supposed to be enough to get pressure up for starting in case it bled down a little over days or weeks. After that, the pump doesn't run until the Engine Computer sees engine rotation, (and develops spark). When you start out with 0 psi, one ignition switch cycle usually isn't enough to get fuel pressure up high enough. Try turning the ignition switch back off, then on a second or even a third time. Each time the pressure will jump up a little more. If you simply try to start the engine, battery voltage is drawn down a lot by the starter motor. That lower voltage means the fuel pump runs a lot slower than normal, so it's less likely to build pressure any faster than the injectors are bleeding it off.

Hope you guys get this solved soon.