SERVICE MANUAL NUMBER 24
DIAGNOSTICS
Chart A-4 (2 of 2): Fuel System Diagnosis
Step
Action
Yes
No
PROCEED TO
Was the “On-Board Diagnostic” (OBD) System Check
Performed?
1.
Step 2.
OBD
a. Install fuel pressure gauge.
b. Ignition OFF.
c. Ignition ON.
d. Fuel pump will run for about 2 seconds. Note fuel
pressure with pump running. The pressure may
drop after the pump stops running, but should not
drop immediately to 0 psi.
2.
Step 3. Step 5.
Is fuel pressure below 25 psi (172 kPa)?
Attempt to start engine and idle at normal operating
3.
4.
temperature.
Did engine start?
Step 4. Step 6.
Step 13. Step 11.
With engine still idling, connect an external vacuum
source to the fuel pressure regulator and apply 10
inches of vacuum.
Did fuel pressure drop by approximately 5 psi (34
kPa)?
Chart
Step 6.
5.
6.
Was fuel pressure present at all?
A-5
Does the system establish fuel pressure and
then drop quickly to 0 psi?
Step 7. Step 9.
a. Ignition OFF.
b. Block fuel pressure line between the fuel pump and
fuel rail (or throttle body inlet fitting on TBI Models)
using fuel shut-off valve tool.
7.
8.
Step 10. Step 8.
c. Ignition ON.
Does fuel pressure hold?
a. Ignition OFF.
b. Block fuel return line using fuel shut-off valve tool.
c. Ignition ON.
Step 11. Step 12.
Does fuel pressure hold?
9.
Check for restricted fuel lines.
Locate and repair leaking injector(s) or fuel line
connections.
10.
11.
12.
Replace faulty fuel pressure regulator.
Verify
–
Repair
Check for leaking pump fittings or lines, inlet filter, and
low battery voltage. If OK, replace faulty fuel pump.
Problem is intermittent or fuel supply to engine is re-
stricted or low.
13.
Index
90-861327--1
OCTOBER 1999
Page 5G-33
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 305 CID, Mercury MerCruiser 350 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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