High fuel pressure issue

[Ed Yez]

New member here. Originally posted this in the Outboard section by mistake.
Just bought a '99 Sea Ray 230BR with a 5.7 TBI Alpha, MEFI-1. When I first bought it, it was running very rich, loading up and would eventually stall. Replaced the MAP sensor and the plugs that were black and sooty. It no longer stalls, but is still running rich. The exhaust still smells rich and the new plugs are black with less than an hour run time on them. Fuel pressure is 34PSI (supposed to be 30) so I replaced the regulator. No change. The excess fuel from the regulator goes back to the filter so I removed the line at the filter housing and ran the return back to the fuel filler with a long hose, essentially bypassing the filter for the return fuel. Once I did that, the fuel pressure came down to 30PSI, where it should be, smoother idle and no rich smell from the exhaust. Replaced the filter and checked for a blockage in the housing, which was clear. Put everything back together and I still have 34PSI. What am I missing? The only thing I can think of at this point is the Sierra filter that's on there is 10 microns as opposed to the Quicksilver's 25 micron. I have the Quicksilver filter on order but I'm not confident that's going to fix this. Any ideas would be appreciated.
I also have a code 42 for the IC module circuit, but that has no bearing on fuel pressure and is a separate issue which I'm working on. Engine has 20" vacuum at idle. I replaced the CTS, IC module and all of the secondary ignition system.
On top of all that, it falls on its face on acceleration, like a carb with a bad accelerator pump.

 

[alldodge]

Having a MEFI 1 and being a 1999 boat, its most likely a 1998 motor. Serial number will verify this?

What did the screen look like under the fuel Reg?

 

[Ed Yez]

Serial number is L091906. Screen was clean.

 

[alldodge]

Thanks its a 1998 motor

The code 42 may be keeping the timing from advancing fully. No advance or less then needed will cause a richer mix.

If ECM thinks the motor is cold it will enrich the mix. The ECT advises the ECM of temp.

Measure voltages a TPS and MAP with key ON motor OFF and with motor running.
Key ON motor OFF
MAP 4.9V TPS 0.5V

Motor running
MAP 1.6V TPS 0.62V

 

[Ed Yez]

CTS resistance checked out but I replaced it anyway as it looked original.
KOEO
TPS 0.51v MAP 4.89v
Running
TPS .51v MAP 1.26v
Regarding the code 42, I went through the flow chart and all the wires checked out. There was some green corrosion on the 4 pin IC module connector so I took it apart and cleaned the terminals. I ordered a new pigtail, but I still have the code 42. I installed a brand new distributor which included the IC module. Set the timing and it ran great, not rich, no lag/hesitation on acceleration. I felt it was fixed so I cleared the codes and on the next startup, it went back to running poorly with the same symptoms.

 

[Ed Yez]

Also, just checked the timing again and it advances to a max of 37 degrees at 2500 RPM.

 

[Ed Yez]

One thing I noticed that looked strange. When throttling up to check the advance, the timing initially retards, then advances. I've never seen this on an automotive engine, not sure if marine should be this way. That could account for the hesitation on acceleration.

 

[alldodge]

Another has same problem with code 42 on OSO with 502 MPI. The ECM should switch apply 5V to switch to IC control. Can also be switching but circuit 423 isn't varying because circuit is open or grounded so code is set

A 10 micron should have no effect on the Reg, and even more so at idle.
30 psi with Reg return not going to filter and 34 psi connected back is a first for me. I would expect line, fitting or housing clog, but you checked it

When key is turned ON (motor not running) and pressure goes up, does it stay up, slowly go down or drop fast?

 

[Ed Yez]

I checked the circuits and they all checked out. Why would it run well on a new distributor/IC module, then go back to the previous condition after clearing codes? Are you saying the ECM is bad? I'm thinking of putting in another new IC module to see if it does that again.

Fuel pressure with KOEO goes to 32 while the pump is running. As soon as the pump stops, pressure drops to 27 and then continues to drop very slowly and holds at 23.
Incidentally, on a cold start fuel pressure is 32 and slowly increases to 34 as the engine requires less fuel as it warms up.

 

[alldodge]

There are different ways the code 42 can come about. Can be caused by a connection or harness issue, control module or ECM. Manaul 24 Page 5G-76 and 76 explains issues and how to troubleshoot

Pressure dropping is probably a leaking injector or so.

There is a possibility that the gauge is not accurate unless other shows the same

 

[Ed Yez]

There are different ways the code 42 can come about. Can be caused by a connection or harness issue, control module or ECM. Manaul 24 Page 5G-76 and 76 explains issues and how to troubleshoot

Pressure dropping is probably a leaking injector or so.

There is a possibility that the gauge is not accurate unless other shows the same

I've done that test many times. Step 4 with the original distributor, the ohms would increase instead of decrease. With the new distributor, the ohms decrease but not below 1000. I've checked those wires, wiggled and pulled with the DVOM attached and they're solid.

I also thought my 25 year old fuel gauge might be wrong so I bought a new one. Same readings with both.

 

[alldodge]

How does step 5 and 6 work out with the test light?

 

[Ed Yez]

Step 3 - dvom connected to ckt 423 (ECM pin J2-23) and gnd. Over 10k ohms - go step 4
Step 4b - just to confirm, I'm using a normal incandescent 12v test light with the clip lead on B+. When I touch the probe to gnd, the light illuminates.
Step 4c - when I contact ckt 424 (ECM pin J2-24) dvom goes to over 12k ohms - go to step 5
Step 5 - test light is still connected to B+ and does not illuminate when touching ckt 424 - go to step 8
Step 8 - there is continuity From ECM J2-24 to IC module 4-way connector pin B - go to step 10
Step 10 - replaced IC module included in new distributor, ran great until I shut it off and cleared the codes, then went back to previous poor running with code 42 still present

Step 6 - test light does not illuminate

 

[jimmbo]

I apologize in advance as this doesn't solve the problem, but Carbed engines are so much easier to troubleshoot when things go wonky. Same goes for Mechanical Advance Distributors

 

[Ed Yez]

I apologize in advance as this doesn't solve the problem, but Carbed engines are so much easier to troubleshoot when things go wonky. Same goes for Mechanical Advance Distributors

Agreed, but I still prefer EFI!

 

[Ed Yez]

CKT 423 during KOEO and cranking has continuity to gnd. Running has 1.2v at idle which increases with RPM

CKT 424 during KOEO has 0v, running has 4.3v

 

[alldodge]

Alpha drive, Circuit 423 white wire goes through shift interrupter with MEFI 1. This is where the ECM makes the motor stumble to shift out of gear

423 should vary based on rpm

 

[jimmbo]

Agreed, but I still prefer EFI!

If I was running EFI, I would always be thinking, 'Okay, I know this Damn thing will Fail, but when?'.

 

[Ed Yez]

If I was running EFI, I would always be thinking, 'Okay, I know this Damn thing will Fail, but when?'.

EFI = no choke to set, less fuel vapors in your bilge, can't vapor lock, fewer moving parts, etc. etc.

 

[alldodge]

can't vapor lock

I'm EFI all the way but yes they can and do VL