Hey all,

I have been driving my built B20VTEC with p28/Hondata s300 for awhile with minimal issues. I had the car sit for 4 days and went to start it...fuel pump does not kick on. my car is a 91 Si and has a Rywire OBD1 harness. Battery is good, and a Walbro 255 installed when the car was built 800 miles ago.

The CEL is constant and does not turn off
Thermostat ground has been sanded and tightened
The Main Relay does not click at all, but fuel pump whirs when I jump the relay

I have tried to research the issue but am getting conflicting info. I am guessing maybe its the ECU. I have a multimeter, but am confused when and where to use it as I am not good with electrical stuff.

Any help is greatly appreciated

 

Update:

I did the 5 volt check on the MAP and it was good. Only now when I put the key in the on position the CEL goes out after about 10-15 seconds. Still no fuel pump kick tho.

 

"The Main Relay does not click at all, but fuel pump whirs when I jump the relay"

Check fuses.
Troubleshoot the main relay.
https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/main-relay-2490241/

 

Replace main relay with a known good working relay aka brand new relay.

 

Update:

I tested the relay per the link and it checks out.

I tried it in On again and after 25 seconds of the CEL being on the fuel pump primed and it started right up so I'm confused.

 

Could be a really weak electrical contact somewhere.
- Check your grounds at the thermostat housing - make sure the wires are looking good and not falling apart.
- When you put your key in and turn to 'ON', try wiggling it back and forth a little. The internals of the lock could be wearing.
- Try a new main relay OR try a repair on your existing relay.

 

This type of problem is now happening more and more often. It's generally a sign that the ECU is bad. This ECU problem may not be revealed by the K-test.

 

Would it show up on a bench test? I bought the ECU from Phearable and he said he benches them before he sells them. The ECu has been in use for about 800 miles with Hondata s300

 

How does Phearable define their "bench test"?

 

No idea. He just said he tests them for sending them out

 

Ask him how he bench tests his ECUs.

I can tell you some tests to perform that may help pinpoint the problem to the ECU or elsewhere. However, based on the symptom, the ECU is likely the cause.

How did you do the K-test?

 

I put the car key in II, removed the map sensor and multi metered thefar right of the map plug and the G101 ground. Got 4.99 volts

 

Do the same test but on the far left pin. Do you also read 5V there?

 

Left side reads 4.69

 

Turn key off.

Unplug ECU connector A. A Grn/Yel wire pins to A7 and also possibly A8 in the unplugged connector. Ground the A7 wire terminal to the metal frame beneath the dash.

Turn key to ON(II).

Does the fuel pump run immediately and stay running as long as the wire is grounded. Repeat the test multiple times.

Do the same test on the A8 pin, if a wire pins there.

Post the results.

 

I'm having a hard time figuring out which spot is A7 since my OBD1 Rywire harness wires are all gray.

 

The link below should help. The pictures show the ECU slots where the connectors plug in. The corresponding pin position in the ECU connector is a mirror image of the ECU picture.

http://www.phearable.net/tech/wiring...schematics.gif

 

Okay I found it. I have no terminal in A8. A7 was grounded and fuel pump runs until I unground it. Did it multiple times.

 

In some cases, there's no wire at A8, but it's normal.

Now plug ECU connector A back into the ECU. Turn key to ON(II). Does the CEL still fail to turn off and the pump fail to prime?

 

It came on after about 15 seconds. In those 15 it was a solid cel

 

Do you have a multimeter?

 

Doing it again 2 minutes after the first, it primed after only 6 seconds

 

Yes

 

Does the engine now start and run fine?

 

Yea its been running, just wondering why its so intermittent on priming