Failed CO emissions - all controls removed - where to start?

[Zed Head]

34 minutes ago, thetwood said:

Other good news is that the car starts up, so I've got that going for me. It's not running smooth now though. Maybe I didn't install the fuel injectors .all correctly? They seemed to go in fairly easily.

With more fuel pressure there will be more fuel through the injectors.  It's probably running rich now, making it run rough.  But that is a common problem with these systems, and solvable.  See if it will stay running after it warms up.  It might die as the engine gets warm.

[Dave WM]

that running pressure is a bit high, prob has to do with poor vacuum, and or vacuum line not hooked up to the fuel pressure regulator.

if it has some wild cam I suppose the vacuum will always be poor or its just the poor state of tune it current in. For now you should chase vacuum leaks. Get a stogie (cheap cigar) and a tube that fits over the large nipple on the intake manifold that feed the brake booster. I like clear tubes so you can see the smoke. Block off the front of the throttle body by disconnecting the rubber boot and put a styro cup over it, you want a good tight seal. Blow smoke into the tube, it may take a while to fill everything up, but you should look for smoke leaking somewhere, there should be some resistance, its not an open system, I actually blew the styro cup off the intake doing this. A flash light is handy to look for the smoke.

you want to get rid of vacuum leaks as that can play havoc with EFI. I am not sure how that filter on top of the valve cover will effect things, I assume there is a PCV valve and I also assume it acts as a check valve if under pressure. Not sure how all that will effect the smoke test.

as ZH mentioned rough running is typical and generally going to have to do with a bad temp sensor.

While you have the boot off (AFM to Throttle body) examine it CLOSELY look for cracks. You don't want air getting into the system that is not going thru the AFM.

Edited October 4, 2019 by Dave WM

[thetwood]

Car will remain running after it warms up, but not happily. Of note, if I remove the cover from the smaller vacuum port to release some of the vacuum, it actually runs a bit better (rpm goes up a bit and doesn't sound as rough). If I open the air flow meter and manually reduce, it runs smoother still...

I removed the AFM. Connector to throttle body seems good. No cracks. I then sealed that, hooked a tube up to a vacuum port and blew in smoke from a cigar. First of all, bleh. Been a long time since I smoked a cigar and I remember why I only tend to do so when drinking...

There does seem to be a small leak in the throttle body. Not at the gasket, but where the throttle goes through the side. Not large (takes a while for to equalize), but does release pressure over 10s of seconds. Is any leaking at all a bad thing? If so, is there a way to seal that section of a throttle body? Or do I get a new one?

Next, I'll start learning how to test temperature sensors. Bought a good mulitmeter. Now just need to learn to really use it (and what to hook it to where...)

[Dave WM]

sounds good, don't worry about a small leak there (throttle plate shaft). Clearly running rich, check the 36 pin connector I think its pin 13 and ground (body chassis). check the FSM to be sure. if the car is warmed up (170ish degrees) you should see about 150ohm IIRC again check the FSM its all in there. IF you get a high reading its prob a defective sending unit or corroded connectors either at the sensor or the bullet connectors of the sub harness OR even a incorrectly connected sub harness. Its easy to swap around the connectors on both the temp sensor and thermos time switch AND the sub harness bullets for both those. That's why its good to check at the 36 pin connector. It will test everything at once, if it test out of spec you can start by simply unplugging the temp sensor, if it reads open then at least you have the right hookups but maybe bad parts or corrosion.

[thetwood]

Will work on that tomorrow. Off to my son's hockey game now. But one quick question. Here's a picture of the sensors as they currently sit. Do I just have the thermotime switch hooked up and not the water temperature sensor? Trying to tell from the FSM, but the picture I found is a bit small.

[Dave WM]

Yep the temp sensor is the small one at 2 o clock. You can get a quick reading on it just to see if its any good as is. Those pins are prob corroded as well. The plug is on the thermo time switch which you don't need since you don't have the cold start valve. My guess is that plug is supposed to be connected to the temp sensor.  should be interesting to see what the resistance readings are at the 36 pin connector. IIRC those two pins on the thermo time switch will be either open (over 65f) or 50ish ohms (cold day, you are reading the heater element resistance). The thermo time switch has NOTHING to do with the ECU, its just like a choke lever that richens up the fuel on cold days to help with starting, Its function is ONLY when the key is in the "start" position and then only on cold days and then only for a limited time (9 seconds) so you don't end up flooding the engine with prolonged start attempts.

Edited October 5, 2019 by Dave WM

[SteveJ]

This picture may help.

[Zed Head]

5 hours ago, thetwood said:

Will work on that tomorrow. Off to my son's hockey game now. But one quick question. Here's a picture of the sensors as they currently sit. Do I just have the thermotime switch hooked up and not the water temperature sensor? Trying to tell from the FSM, but the picture I found is a bit small.

Yes, your coolant temperature sensor is not connected n that picture.  Easiest way to tell them apart is that one is big and one is small. The thermotime switch is big.  Looks like new wires also so make sure you know which plug is for which terminal.

Your engine should not run for long with that disconnected.  The fact that it does suggests vacuum leaks and/or low fuel pressure.

[thetwood]

OK. A few questions that I know are basic for you guys, but the electrical systems and testing electronics is all new to me.

1) Is there somewhere in the FSM that shows the ECU and which pin is which? I've been looking through and either am not finding it or just don't know how to read it correctly...

2) With the temperature sensor disconnected, should I get an ohms reading by testing the two pins in the sensor?

3) The pins in all of these sensors are corroded. What's the best thing to use to clean?

[SteveJ]

1) Go to the Files section here (see the link in my signature) and download the 1978 FSM. The EF section has the information you're asking about. For the pinouts, look at EF-22 through EF-24.

2) I do not recall specifically, but component tests are in the EF section. I might be nice and find it for your, but the World Cup Rugby match is about to come on TV. (Priorities!)

3) I like a dremel and wire wheels. Coat anything you clean with dielectric grease to slow down corrosion.

Edited October 6, 2019 by SteveJ

[siteunseen]

Dumb question, duh it's me, why is his connectors pointing towards the distributor and not the radiator? Optical illusion or maybe I stayed out too late last night.

[SteveJ]

45 minutes ago, siteunseen said:

Dumb question, duh it's me, why is his connectors pointing towards the distributor and not the radiator? Optical illusion or maybe I stayed out too late last night.

It's the "Batman angle" of the photo that's fooling you.