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I checked the vacuum on the egr valve earlier & it holds a vacuum very well and can see the diaphragm moving. Been troubleshooting the truck 1993 f150 4.9L 6 cylinder 4 weekends now. 350,000 miles and recently hard to start. Need to crank the engine four times 6 seconds each time & the fifth time starts. Replaced the fuel filter, spark plugs (the year old ones looked good) spark plug cables, map sensor, check battery, alternator, starter: all good.
Engine idles & runs smooth at all speeds, going up hill or Hartman Bridge with AC on max. Problem does not get any worse. Took to dealership and independent mechanic: no check engine light or fault code and they are not sure. 18 hg at idle & 50 psi fuel pressure. Healthy spark while cranking using a HEI spark tester. Any clue?
Engine idles & runs smooth at all speeds, going up hill or Hartman Bridge with AC on max. Problem does not get any worse. Took to dealership and independent mechanic: no check engine light or fault code and they are not sure. 18 hg at idle & 50 psi fuel pressure. Healthy spark while cranking using a HEI spark tester. Any clue?
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Posting Guru
Joined: Jan 2004
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From: Charlestown, RI
The EVR (exhaust vacuum regulator) switches under certain conditions, to apply vacuum to the EGR valve. Normally when the EVR fails, it applies vacuum to the EGR constantly, which will affect your idle all the time. It doesn't sound like this is your problem.
Having to crank 4 times like that, it almost sounds like the fuel system isn't holding pressure when the truck is shut off. Best way to find out is to attach a fuel system pressure tester to the fuel rail, and leave it overnight.
Having to crank 4 times like that, it almost sounds like the fuel system isn't holding pressure when the truck is shut off. Best way to find out is to attach a fuel system pressure tester to the fuel rail, and leave it overnight.
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Hello Bob
Thank you Bob for the suggestion. Several times I have left the fuel gauge on the fuel rail after turning off the engine and I takes about an hour for the gauge for the pressure to drop to 35 psi. When I crank the engine the fuel pressure immediately is 50 psi. Are you suggesting the fuel pressure should always be a constant 50 psi?
Posting Guru
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From: Charlestown, RI
Yes, the fuel pressure shouldn't drop when the truck is shut off. While 35 psi building back to 50 immediately wouldn't be a cause for concern, it may drop further down overnight, and take longer for the truck to crank over in the morning. "priming the fuel system" sort of action. 
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Joined: Aug 2005
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From: Easton,Ks
Thank you Bob for the suggestion. Several times I have left the fuel gauge on the fuel rail after turning off the engine and I takes about an hour for the gauge for the pressure to drop to 35 psi. When I crank the engine the fuel pressure immediately is 50 psi. Are you suggesting the fuel pressure should always be a constant 50 psi?
50psi is OK at idle but not while cranking or at WOT.
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hddave44
1987 - 1996 F150 & Larger F-Series Trucks
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Apr 4, 2015 02:44 PM