Question about CAS

[BpuVR4]

so diagnosing another no start. my question is regarding the CAS. Ive verified I have spark, but im wondering if the CAS can allow spark but not fuel? Or if it's bad it won't allow neither? I can't even smell fuel in the exhaust while cranking, fuel lines feel full also. Back of my mind wonders if my fuel pump died already after installing in late Oct. I did notice going to the new 190 pump, it took a couple extra cranks to start the motor.

just to verify on testing the fuel pump via connector, i can hook up alligator clips from the plug to the positive of the battery, then try to start the car?

Have swapped to back up ecu, mpi relay and cas. My car is currently cozy under a foot or so of snow, damn chicago weather. Car ran perfect when i parked it..may have done a couple harder pulls, but idled fine, and shut off fine. Came out next day and i get this.

 

[strokin4dr]

If you do not have a fuel pressure gauge, I would crack open a line to see if there is pressure. If you have spark and no fuel, AND the pump proves to be good with jumping the connector, you most likely have a bad fuel pump relay.

 

[BpuVR4]

is there a separate fuel pump relay other than the MPI relay? i feel like i got mixed info on this the last time i had to check.

 

[G]

Loosen the cas and try starting the car while someone slowly rotates the cas up and down and see if it starts.

 

[BpuVR4]

Ill give that a try tomm w 2nd set of hands. Cleaned snow off tonigjt and took off the return fuel line off the rail, nothing came out as I cranked.

I checked the mpi fuse, was good.

Can hear mpi relay click after shutting off.

How good does the connection on the fuel pump test port have to be? Im using a small gator clip going from batt positive post, but im not sure if its in the plug enough.

Gonna try to have whatever electrical pieces tomm- cas, mpi, and even gonna pull the fuel pump...anything im missing?

If I find pumps out already ill be pissed

 

[turbowop]

Just use a spade connector to connect 12v to the fuel pump test lead connector. Find somebody local with a spare CAS to try out as well.

 

[BpuVR4]

Ok thanks about spade idea, was thinking paper clip but that obv better idea. I have a spare cas I swapped...they do same thing. Gonna have them tested on multimeter again tomm also

 

[Wizardawd]

easier way to check the CAS is to just remove it from the head, leave it plugged in. Turn the key to ON and turn the CAS by hand. Listen for the fuel pump, injectors and spark plugs firing. If you hear nothing, replace with another and repeat. Easy to do by yourself that way.

If you hear the injectors clicking and the plugs firing, the CAS is more than likely fine.

Then do the fuel pump jump. Use a multi-meter and check for voltage at the thick black/white wire at the fuel pump assembly. If you are getting power to the pump, but no fuel....you have your answer.

Wiz

 

[BpuVR4]

wil give this one a try first thing tomm.

 

[BpuVR4]

i hand tested the cas, got spark and heard the injectors fire.

had my friend test the fuel pump out of the car, it works

he located the problem to a square black relay behind the trunk trim- is this the fuel pump relay?

 

[turbowop]

Did somebody do a fuel pump rewire on that car previously? That's probably what the relay in the trunk is for. They're cheap enough if it's just a Bosch relay, replace it and see what happens.

 

[BpuVR4]

yea this car came with an ugly rewire already. guess thats my next stop...didn't know they hid these things back here.

 

[BpuVR4]

went to the Advanced Auto by me and they didn't have anything. its a small squre 4 prong relay 12volt 30amp one. im assuming this is part of the rewire kit. wish i could upload a pic, but im having right click/save image problems w my computer right now.

but it looks like this one:

click

 

[Wizardawd]

Usually you find a relay all by itself in a package at the store with the fog lights. Around $8.00 or so.

Wiz

 

[G]

Radio shack.

 

[BpuVR4]

thanks guys, got a new relay, and now im stumped.

-installed new relay. won't start.
-will start when the relay is jumped on two prongs- fuel pump will run.
-black wire connected to the relay is a ground.
-the black wire taken off to be jumped goes to the pump.

any takers? pic of relay

 

[G]

 

[BpuVR4]

thanks for the diagram G.

 

[BpuVR4]

just so i'm covering all my bases here, these are the parts that will send/help send a run signal to the fuel pump:

-ecu
-cas
-mpi relay
-mpi fuse

any other components that is responsible for making the pump run?

I've had some great help from Toybreaker who was generous enough to give me a wealth of help via phone on this. John has suggested to dig deeper into the fuel pump rewiring and relay.


I've also had help from my friend who is great with electrical- but we live in different towns and he just started a family). and my friend has told me that he believes somewhere else there is a part that is not causing the pump to run. He's claiming the fuel pump is not receiving a run signal until the car is running- i told him that on our cars the pump doesnt start running until the motor turns over, however not sure if we're talking about the same thing. I thought that I exhausted the list of parts that would be responsible for that but just wanted to make sure.

current state of car: if the two prongs on the fuel pump rewire relay are jumped (like in pic above), the car will start and run.

 

[toybreaker]

... sorry I havent gotten back to you, been shovelin a bit.


I think you grasp the whole principle of how it all works just fine.

Basically, the wire that you have unplugged from the aftermarket relay in the pic is the black/white wire that originally ran from the mpi relay out to the pump. It now runs to T86 of your aftermarket relay and is used as a trigger to turn that relay on.

Since the pump runs with the relay jumped, it's time to check to see if the mpi relay is doing it's job.

It's "looking" for the ecu to authorise it run the pump, (by grounding one leg of the mpi relay coil) and the ecu is "looking" for a cas signal to authorise the mpi relay. ( frequency signal that also runs the tach)


That stuff is kinda involved to check properly, lets try a few simple tests before we get all scientificall






A quick test is to put the positive lead of a voltmeter into your loose wire, ground the other test lead, and crank the engine.
> should have ~12v while cranking <

Also, watch the tach needle
< it should "bounce" while you're cranking <

Those two tests will give enough information to decide where to go next.


Good luck, and I'll try and catch up with you later



... still shoveling ...