'87 fuel problem
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
'87 fuel problem
Friend's 87 has following problems:
Takes 5-10 seconds of cranking before starting...but not all the times.
Checked fuel pressue: pressure only came-up to about 30 and did so slowly with the key turned to ON. Cycled key again and pressure came up to 43 or so...engine started. Pressure holds around 40 with engine running.
Turn engine off; pressure drops immedately to about 30, holds for several seconds, then drops to zero.
Replaced fuel pump with a Delco unit. No difference. Checked regulator - diaphram is fine, no fuel in vacuum line. Fuel filter was replaced 3-5 years ago. Car runs okay once started.
Where is the check valve that holds the pressure in the fuel system located? I thought it was in the fuel pump.
Any ideas????
Takes 5-10 seconds of cranking before starting...but not all the times.
Checked fuel pressue: pressure only came-up to about 30 and did so slowly with the key turned to ON. Cycled key again and pressure came up to 43 or so...engine started. Pressure holds around 40 with engine running.
Turn engine off; pressure drops immedately to about 30, holds for several seconds, then drops to zero.
Replaced fuel pump with a Delco unit. No difference. Checked regulator - diaphram is fine, no fuel in vacuum line. Fuel filter was replaced 3-5 years ago. Car runs okay once started.
Where is the check valve that holds the pressure in the fuel system located? I thought it was in the fuel pump.
Any ideas????
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Bad check valve in the fuel pressure regulator, or a leaky, stuck injector/s. My 87 this past summer I had to crank 3-4 times to start. One day I went WOT to get around an idiot and from then on it started normally on one short crank. I think I had a stuck injector. My fuel pressure would go instantly to about 35 psi, but fall instantly when the fuel pump turned off.
If you have the original fuel injectors, then my vote is for defective injectors.
If you have the original fuel injectors, then my vote is for defective injectors.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
You also have a pulsator, that can cause loss of fuel pressure.Alot of guys have replaced it with simple fuel line and clamps. Pinch off your fuel return line and see if pressure holds. On my 87 the pressure came up to 40#s when the key was turned on, when off the pressure slowly dropped to around 30#s and held there for over half an hour, I said good enough.
Try ohming your injectors, although the FSM says they should ohm above 10, mine ohmed around 16 +/- .5 if I remember right.
And it's definetly time to replace that fuel filter.
I wouldn't hesitate to replace the fuel pump relay either (relays can be intermittent)., there about $10-12 bucks.
Try ohming your injectors, although the FSM says they should ohm above 10, mine ohmed around 16 +/- .5 if I remember right.
And it's definetly time to replace that fuel filter.
I wouldn't hesitate to replace the fuel pump relay either (relays can be intermittent)., there about $10-12 bucks.
Advanced
Joined: Feb 2008
Posts: 98
Likes: 0
From: Southlake Texas
replace the fuel pressure regulator. Pressure should be 36psi when running and hold for a long time when shut off. The vacuum line is for enrichment under accleration and pressure should go to about 45psi under vacuum. How accurate is your test gauge? I use a 4" diameter gauge for easy reading on the 1 pound increments. Could be an injector, but cycling on and off like you say seems more like a bad regulator.
Intermediate
Joined: May 2008
Posts: 38
Likes: 1
From: Yuba City CA
I replaced my presure regulator and had a second problem. On the '87, there is another fuel injector on the driver side which is your cold start injector. This will cause excessive cranking. I "think" in later years, they did away with it and just widened the injector pulse at start up.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
cold start injector
cold start injector drops out if the temp sensor (cold start valve) senses that the engine is warm. This is not a computer function.
Check when cold that the temp readout reads LO. If so, you should be guaranteed that the cold start injector will be turned on.
The valve should provide the full time alotment. It only is on for about 8-10 seconds. A warmer engine but not warmed up engine will see less time. otherwise, the cold start injector is not turned on.
If the engine starts differently either hot or cold, then each scenario should be investigated.
Check when cold that the temp readout reads LO. If so, you should be guaranteed that the cold start injector will be turned on.
The valve should provide the full time alotment. It only is on for about 8-10 seconds. A warmer engine but not warmed up engine will see less time. otherwise, the cold start injector is not turned on.
If the engine starts differently either hot or cold, then each scenario should be investigated.
Last edited by coupeguy2001; Oct 20, 2008 at 10:46 PM.
Melting Slicks
Joined: Mar 2008
Posts: 2,453
Likes: 346
From: SC
Just taking a shot here....but could it have anything to do with VATS? I had long cranking on my 87 2-3 seconds. I noticed the chip in one key was different than the other ignition key. Since using the newer key fires it right up. I cleaned both keys with alcohol and now both fire right up. Maybe just a coincidence but maybe a bad contact was the cause?
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Just taking a shot here....but could it have anything to do with VATS? I had long cranking on my 87 2-3 seconds. I noticed the chip in one key was different than the other ignition key. Since using the newer key fires it right up. I cleaned both keys with alcohol and now both fire right up. Maybe just a coincidence but maybe a bad contact was the cause?
Tried that couple of times. Got new key, cleaned ignition cylinder....no change. But did find the clutch safety switch had a problem at times.
Besides the VATS wouild not allow the starter to engage.
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