hard start cold---fuel prob i think

[brutis5]

97 4.3 blazer.......I got spark,it turns over, fuel presure reads 60,but no start. spray starter fluid, car starts runs rough for a min then starts running fine. after 1st start of the day starts ok with short time between starts. wait 6 hours or so, starts but with some cranking. wait over night, no start. pump was replaced a year ago, not that it would matter, but its not the original. I also did a test----turn key to start pisition, listen to pump run until go's off then crank for a sec. release key to on position but engine off, wait til pump turns off again then crank and it starts, why!!!! anybody got any ideas, i could use the help. thanks

[old_master]

Classic low fuel pressure symptoms. Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After 2 to 3 seconds, the fuel pump will shut off and the fuel pressure must remain above 55psi for 3 to 5 minutes. Check it and post your results.

[brutis5]

did the test . the 3-5 min test drops to 45lbs. and i left the pressure gauge on over night and it was 0 lbs. as sone as i turn key on i gos up to 60lbs but it just cranks. will 45 lbs at inital start keep it from starting. and you said classic case of low presser. whats the classic fix? pump or under top of intake issue. thanks

[old_master]

Your pressure test confirms you have excessive leak down. It does not diagnose what is causing the leakdown. At this point it could be the pump or something under the plenum. To determine where the leak is, the pump must be isolated from the rest of the system while the system is pressureized. That requires a shut off valve to be temporarily installed in the fuel pressure line. If the pressure holds, the pump is leaking, if it drops, the problem is under the plenum.

[DelCoch]

A weak battery will cause the starting problem you’ve described. Will crank over fine, but the starter takes all the current away from the fuel pump not allowing the fuel pump to reach max pressure, which is needed for a cold start. Once the engine is running the battery will charge up some and the engine will start until it sits and the battery becomes weak again in about 6-hours. 60 psi is very marginal for a cold start. Most say it should be between 61 to 66 psi.

Check the battery with a load type tester or take it to AutoZone, etc., they will check it for free. If battery is ok then I would disconnect the fuel filter, (should be located on the inside of the frame under driver’s door) and with an adapter, connect your fuel pressure gauge to the line coming from the fuel tank. See what kind of a reading you get for fuel pressure at this location and if you still have the leak-down.

You didn’t say what name brand fuel pump was used in the replacement, but if it was an Airtex, chances are it has gone bad again. Bosch or Delphi is the only way to go with fuel pumps. From what I've seen and heard, Airtex is crap!