Intermittent no start...fuel pump???

[wpurple]

Last few days I have gotten an intermittent no start, my gut says fuel pump.

I spent some time today diagnosing since it was in a no start condition.

-Getting spark
-Swapped fuel pump relay
-Sprayed starting fluid and it fired off

After fiddling with it for a while it started and ran fine, even ran some errands. This happened the other day wouldn't start then after a while it did and ran fine all day

Is it possible that a bad fuel pump can be that intermittent? I do hear the fuel pump prime even when a no start...

I assume that the fuel pump runs 100% and isn't PCM'd as the scan tool always showed duty cycle of 100%, unfortunately I did not see a way to monitor fuel pressure.

-Thanks!

 

[J_C]

There should be a schrader valve on the fuel rail to check pressure. Autozone, Advance Auto, etc offer free loaner tool pressure gauges (with a deposit).

Yes on your return type fuel system, the pump runs 100% and there's a fuel pressure regulator on the end of the fuel rail, regulating to around mid 30's to low 40's PSI and excess pressure is bled off to the return fuel line going back to the tank.

Yes a bad pump can easily be intermittent, and while less common, the pump can spin at too low an RPM and not generate enough pressure. Since you have a '97, it is unlikely that it has the PATS security that disables the fuel injectors, so this leaves power not getting to the pump (bad contacts or wiring), or pump itself. Pressure regulator, fuel cutoff safety switch, or clogged fuel filter might be suspects if it never started or didn't run well under throttle when it does, but we can probably rule those out in this intermittent starting case.

It is most likely the fuel pump itself, but I wouldn't ignore wiring and connector contacts after ~27 years of service.

 

[wpurple]

There should be a schrader valve on the fuel rail to check pressure. Autozone, Advance Auto, etc offer free loaner tool pressure gauges (with a deposit).

Yes on your return type fuel system, the pump runs 100% and there's a fuel pressure regulator on the end of the fuel rail, regulating to around mid 30's to low 40's PSI and excess pressure is bled off to the return fuel line going back to the tank.

Yes a bad pump can easily be intermittent, and while less common, the pump can spin at too low an RPM and not generate enough pressure. Since you have a '97, it is unlikely that it has the PATS security that disables the fuel injectors, so this leaves power not getting to the pump (bad contacts or wiring), or pump itself. Pressure regulator, fuel cutoff safety switch, or clogged fuel filter might be suspects if it never started or didn't run well under throttle when it does, but we can probably rule those out in this intermittent starting case.

It is most likely the fuel pump itself, but I wouldn't ignore wiring and connector contacts after ~27 years of service.

Thank you,
Correct, I do not have PATs system.
Great idea about fuel pressure gauge, I was going to just see if fuel squirts out when in no crank mode, but by the time I got to wanting to do that, it started and ran. (ran a short errand and no issues)

Just ordered one on Amazon, great tool to have on hand.

 

[wollimann]

OTC 5630 a good pressure gauge, comes with the small fuel rail adapter.
At the end it is always the fuel pump and the cracked short rubber hose.
Use a good pump (Bosch, Quantum,...).
Rarely read about a bad fuel pressure regulator.

 

[J_C]

Rarely read about a bad fuel pressure regulator.

True but every year these get older... unfortunately there's no aftermarket support for '97-98 FP regulators, have to cobble something together if it goes bad.

 

[wollimann]

Bosch 0 280 160 554 or Volvo 9146761, only have to cut the return line and clamp it down.

 

[wpurple]

..meant to add, when it does start and run it is fine...think it will take more troubleshooting to make a conclusion, unfortunately, being intermittent it makes it difficult and also not wanting to get stranded. Not venturing too far away from home and also trying to use as much fuel as possible as tank is full.
Also when temps warm up (11 deg here thiis morning) can do more inspection.

 

[Turdle]

Next no start, try fuel pump prime 4 times, key to on, then 5 the try turn key all the way to start. If this works, fuel pump for sure.

 

[Pete Deering]

Last few days I have gotten an intermittent no start, my gut says fuel pump.

I spent some time today diagnosing since it was in a no start condition.

-Getting spark
-Swapped fuel pump relay
-Sprayed starting fluid and it fired off

After fiddling with it for a while it started and ran fine, even ran some errands. This happened the other day wouldn't start then after a while it did and ran fine all day

Is it possible that a bad fuel pump can be that intermittent? I do hear the fuel pump prime even when a no start...

I assume that the fuel pump runs 100% and isn't PCM'd as the scan tool always showed duty cycle of 100%, unfortunately I did not see a way to monitor fuel pressure.

-Thanks!

When you turn the key( ignition switch), do hear a click?

 

[410Fortune]

Fuel pressure at the fuel rail schrader valve should be 36-42 psi