Slow to first start, perfect thereafter -- any ideas?

[lobo411]

So I've noticed that my 1996 4.0 OHV 163k has begun taking a while to catch on first start over the last year. It used to fire up in 2-3 seconds, but the first start is often twice that now. It doesn't seem to be dependent on temperature (SoCal anyway, so the morning ambient temp range is usually 50-60 degrees F year round). Usually, I start the car for the day, drive it 3/4 mile to the Post Office, shut it off and do my biz, then come out and drive it 4 miles to the gym. The second start and every other start is always practically instant. No problems at all.

It's running great otherwise, no codes, just passed smog with flying colors, 20 mpg highway/14 city, etc... I always allow the fuel pump to load for a sec before cranking, but I tried doing that 2-3 times before first start to see if it was a fuel pump problem. Didn't help any. I do have a slight cooling system leak that seems to be leaking externally from the head gasket down the block, but it's very slow and there are no signs of a head gasket issue besides dried coolant in that area/needing a 1/2 cup of coolant every 2-3k mi.

Any ideas? I changed the fuel filter, and I've been doing a slow-motion tune up over the last 2 years--new plugs, wires, cleaned the MAF/IAT, tried Techron, etc... The IAC valve seems to be working fine so I haven't touched it. The car idles smooth and steady, right where it should be on the tach. No codes.

I have to say it does kinda sound like it might be fuel, though, because it cranks good and strong. It's kind of like the first start right after changing the fuel filter--it cranks for a bit longer b/c there's no gas in the line.

Thanks for any possible leads!

 

[koda2000]

at 163k, my guess would be fuel pump.

 

[2000StreetRod]

Ford Explorer Ranger Fuel pressure test procedure

I agree with koda2000:
Ford Explorer Ranger Fuel pressure test procedure

Other possibilities: fuel pressure regulator with leaking diaphragm, defective engine coolant temperature sensor, wet spark plugs from blown head gasket

 

[lobo411]

Thanks for the tips guys! I think I passed the fuel pump test. I dug the brand spankin' new Harbor Freight fuel pressure test kit I inherited from my Dad out of the garage (I had mistakenly thought it was the kind you could only use on a non-fuel injected fuel system) and had a run at it. Here are the results:

Cold engine--last start was 24 hours ago:
Key on engine off:
Initial: spike to 40 PSI, dropping to 36/7 after an instant
5 min later: 34 psi

Key on engine running:
At idle: 30/32 PSI
At 3000 RPM: 30 PSI
After backing off on throttle: Brief drop down to 28, then back to 30 psi

Shut down the engine and disconnected/plugged the fuel pressure regulator vacuum, restarted:

Stayed at 40 PSI the whole time no matter what I did: idle, 3000 rpm, etc...

And *OF COURSE* it started up in an instant on first start. Like any machine, it *KNOWS* when you're trying to figure out what's wrong and absolutely refuses to repeat the behavior when you've got a test instrument on it! ;-)

I guess it can't hurt to pull the plugs on the side with the leaking head gasket and have a look. Luckily, that's the "easy" bank!

 

[2000StreetRod]

fuel pressure looks good

I agree that your fuel pressure looks good. I suggest that you perform a compression test on the cylinders that you remove the plugs from.

 

[lobo411]

I agree that your fuel pressure looks good. I suggest that you perform a compression test on the cylinders that you remove the plugs from.

Thanks! I found the compression gauge but the rubber lines were all cracked (this is stuff I inherited from my Dad...the kit is so old, it's made in America! Really nice proto gauge though). So I just pulled the plugs...they don't look so great. These are Autolite Double Plats that were installed in January and have less than 3000 miles on them. I changed the plugs because the engine was pinging on steep grades, but it didn't help:

The worst plug of the Driver's side bank: This is the cylinder nearest the a/c compressor. I was surprised to see so much glazed carbon. I had a valve job done with new valve seals/guides 50,000 mi/10 years ago, but maybe they're leaking?

This is from the middle cylinder, which is the one nearest the external coolant leak. Still has some glazed carbon on the opposite side, but not as bad. I'm wondering if the grey ashy stuff here indicates coolant:

This is from the cylinder nearest the firewall. Still has a little carbon, but the plug is the cleanest of the lot.

Finally, here's a pic showing the external coolant leak. The trail starts at the junction of the head and the block where the oil dipstick tube is located, and goes down the block towards the starter motor. The consistency of the deposits is like petroleum jelly, so I guess the coolant is mixing with oil from another external oil leak. My engine oil is good and clean, though.

 

[2000StreetRod]

plug gap?

What is the gap on those spark plugs? Looks to me like it might be excessive.

 

[lobo411]

What is the gap on those spark plugs? Looks to me like it might be excessive.

I didn't check the first time (sun was shining on me...I hate the summer!), but I pulled one again just now and it's .053". The gap looks much larger in the photos, but I think it's an optical illusion.