[Chubby Bunny]

Ever had one of those Saturdays when you start on a seemingly simple task that ends up taking all day?

I am still trying to diagnose code 1 (oxygen content) and wanted to start at the very beginning with the fuel pressure check (page 11-96). The car runs and drives great. Rented a test kit from Autozone and tested this morning. Initially the gauge showed some pressure but after I bled off the pressure, it remained mostly at zero, not only after priming the system several times but also while idling.

I then rented another test kit from Oreilly with the same results. Initially, the pressure went up to 40 with the key in the on position but after that nothing. Car still started fine but the gauge read just above zero. "Impossible" I thought. It needs fuel pressure to run. Must be the gauge. But two separate gauges?

Then, while idling, I decided to clamp the return line with the following result:

PSI gradually increased to 33 PSI and stayed there with vacuum line connected and return line unclamped. Disconnecting return line caused pressure to rise slightly. Pinching return line caused pressure to increase to near 36 psi.

Second gauge:

Pinching return line caused PSI to climb from 0 to 36 psi before settling to 34-35. Disconnecting vacuum line had no effect on fuel pressure.

According to the manual, the operating range is between 35-41 psi.

After shutting the engine off, pressure dropped by 4 psi in ten minutes. No leaks at the rail. No evidence of leaky injectors.

I'm thinking of replacing the regulator but they're kind of spendy. I just don't understand why I got a zero reading at idle?!?! It had to have pressure.

 

[joelidge]

Where did you connect the gauge? I assume you put it between the fuel rail and the fuel filter. If you put it between the regulator and the return hard line you would expect see this type of behavior. Otherwise, it would appear there is an issue with the regulator.

If you had the return line pinched and removed the vacuum line, nothing should happen. The regulator cannot regulate pressure in a returnless system.

Maybe your injectors are stuck on which would drop the pressure or maybe the regulator is bad. I would test the regulator by removing the return line, connecting the gauge between the fuel filter and fuel rail, then priming the system with the return line in a gas can. If you are seeing fuel dump out and zero pressure without the injectors firing, it's highly likely the regulator is bad.

 

[Chubby Bunny]

Thanks for the tip. I did as you said, except for substituting an empty can of Campbells Chunky Soup. I primed it four times and got about 3 ounces of fuel in the can. So I guess that means regulator. Though I'm still surprised it ran as well as it did.

The gauge was connected to the outlet port on the fuel filter, per the manual. I don't think the injectors are stuck because the plugs looked normal and were all dry.

 

[mossin_90]

Is the fuel filter new?
New fuel pump?

A Clogged up fuel system will not read full pressure giving you the impression the FPR might be bad.

 

[Chubby Bunny]

New filter. Don't know about the pump. Car runs fine.

 

[mossin_90]

How are the spark plugs center ceramic electrode color?

Bright white = running lean.

Light brown is ok

A dark color = running rich

 

[Chubby Bunny]

They seem ok.

 

[jwharnish]

They seem ok.

View attachment 2338

plugs look ok. Regulator seems to be issue. May be intermittent issue. Checked vacuum line going to regulator? You did mention 4 psi loss after 10 minutes. Pump issue car would not run.

 

[Chubby Bunny]

OK, I just replaced the regulator with no difference. Both gauges continue to show zero psi with the engine running. Again, the pressure only built-up after pinching the return line. Also, no change in PSI when I disconnected the vacuum line. And the CEL still comes on (codes 1 and 14) after the car warms up. Car runs and starts fine. Feel like I'm chasing ghosts. Maybe low vacuum?

Also, the two codes appear to be simultaneous - not separate, which I think means they're related. I didn't get any codes before the D16A6 swap. Things that have changed are the ECM, O2 sensor, manifold, and cat (there is none).

Next, I will try to test vacuum next and re-check the O2 sensor voltage and resistance to the ECM.

My gut says it's just an old car and there's not anything majorly wrong, get over it. It's just annoying and we'll never know if new faults are detected (unless I periodically check the LED).

 

[mossin_90]

are you using the A6 ecu or the HF. What code is it?

Idk if its the light but the last spark plug on the right looks darker than the last on the left.

Any chance the fuel tank was cleaned up before the swap? Specially if the car sat for a while.
If the fuel filter was bad the fuel pump strainer is not going to be that far behind either.

 

[Chubby Bunny]

It's a PM6 that came with the donor engine. I wish I had one lying around to swap-out.

The #1 plug has some oil on it.... looks like some oil is getting past the donut.

Never touched the fuel tank. The car did sit from around April to November.

 

[jwharnish]

It's a PM6 that came with the donor engine. I wish I had one lying around to swap-out.

The #1 plug has some oil on it.... looks like some oil is getting past the donut.

Never touched the fuel tank. The car did sit from around April to November.

you still have HF ECU? I'd swap in old HF ECU and restart. I believe this should at least give you a look with different ECU. I think HF unit should work for testing, unless someone knows different.

 

[mossin_90]

OBD0 is not accurate.

The O2 sensor reads static electricity produced inside the tip.

if the fuel pump is weak the fuel will not be atomized correctly giving a different exhaust gasses temp.

A bad gasket/ seal on the intake manifold, fuel delivery out of specs, bad ground, broken wire, cable with bad insulation, bad ecu, and several other conditions will trigger that code.

You need to diagnose one by one until you find the cause of the code.

Gl

 

[Chubby Bunny]

you still have HF ECU

Sold it on ebay. :-(

 

[jwharnish]

Sold it on ebay. :-(

Dang, got to keep some of those old parts that still work. Have an attic full of stuff I've collected over the years. Have three d16 ECU's I'd offer up but won't be home for a month. 2 chipped, one stock.
One other thing you mentioned that doesn't make sense is the 0 pressure readings. Even with a bad regulator I do not think you would be getting 0 readings. A 0 pressure reading makes me wonder about the fuel pump. Blocking off the return line increases pressure like it's suppose to, but getting a 0 reading seems more like a fuel pump issue that's intermittent. Do a fuel pump check, that's something you can hear working or not. Check the plug going to the pump under the rear storage tray. Ground also.

 

[Chubby Bunny]

Have three d16 ECU's I'd offer up but won't be home for a month.

It might take me a month to do all of the other checks.

 

[Chubby Bunny]

This is a great video on CRX fuel system troubleshooting. He used the same Autozone test kit as I did. I did the exact same procedure and got no reading after start-up.... with two different kits. The difference being that his car was running rough but flashes no codes. Our car runs fine but flashes CEL codes 1 and 14. I'm going to do more checks today.

 

[Chubby Bunny]

Checks for today so far:

• Tested manifold vacuum. Almost 20 inches at sea level. Goes to zero when I blipped the throttle. So no vacuum leaks.
• No resistance from the block to the negative post on the battery.
• Checked fuel delivery. About 5 ounces in 10 seconds. According to the manual, it should put-out 8 ounces, (at the return line - not the filter. It does seem to loose some pressure pressure when the car sits for a while, which could be the check valve. But I don't think that would cause low pressure.
• Checked voltage at the 02 sensor, which should be between .1 and .9 volts, which it was. However at idle, it tended to stay at the upper end of the range, around .78 and then it would slowly count down to the high .6's. Which means rich.
• I also checked continuity from the o2 sensor plug to ground. The multimeter would beep but when I set it to ohms, it didn't seem to register.

Wish I knew what specifically causes the ECU to throw the code.

 

[Chubby Bunny]

Today I swapped-in another PM6 ECU and got the same code. At least it's one more thing off the list of possibilities.

 

[jwharnish]

Today I swapped-in another PM6 ECU and got the same code. At least it's one more thing off the list of possibilities.

Real head scratcher with this one. On my 96 hatch I thru a code once with a bad gas cap seal. Not sure if anything was in place in 88 for this type of issue. What brand on the O2 are you using? Also be interesting to see what voltage from O2 is at ECU plug. You indicated you checked this at O2, but what is it at ECU? Just trowing this out at this point. How are you clearing out codes between testing?