K87ZZ4

Twice today, my 87 started, but ran *very* rough and wouldn't accelerate. I could smell fuel, too. The other times it started fine. I searched through the forum and it seems likely to be a fuel issue. Top sources are likely fuel pump, regulator, filter or injectors.

I drove it about 30 minutes this morning, shut it off for 30 mins, then drove 10 mins. Shut it off for 30 mins, then it started rough and wouldn't accelerate. I shut it off, quickly started again (I was in the street!), still running rough. Shut it down for maybe 30 secs, started again and it ran fine/normal for the 20 mins ride. Sat for 4 hours. Started fine and drove it for 30 mins. Sat for 2 hours. Started rough. Shut it off and tried again, still rough. Let sit for about 1 minute, started and ran fine/normal for a 30 min drive home.

Someone suggested pulling the vacuum line to the regulator to see if fuel is present (shouldn't be). The regulator is under the plenum, right?

I don't yet have a fuel pressure gauge, but I'm long overdue to get one. I'm thinking that's where I should start. Does that make sense? Does it just tap into the schrader valve?

As always, any help would be most appreciated!

ex-x-fire

Yeah, it helps you see if the pressure is bleeding down, if the regulator is working, & if the pump is getting the pressure up to spec.

joe paco

if you smell fuel, and if the regulator is leaking fuel, the leak goes into the plenum, via the vac line on the FPR. it is a rich condition -of course. if the issue is lack of fuel delivery, that is a lean issue.

have you checked for codes? I believe the 02 sensor would set a code 44 or 45. it is intermittent so I doubt it is FPR leaking which would leak all the time.

if no codes try unplugging MAF sensor to see the reaction, while it is running rough. may not be fuel related, or if it is it may be lack of fuel, fuel filter clogged, pump issue, etc. the gage will give you a clue.

any of the normal issues with ign system, high voltage leak to ground, etc, cause the same symptoms.

65Z01

First check for stored trouble codes:
-insert ends of paper clip into ALDL pins A & B (two upper right)
-turn on ignition
-count the SES flashes and record any non-"12" codes
They begin with "12", proceed with each trouble code, end with "12".

K87ZZ4

My mechanic suggested a test for that... run the car, shut it off and pull the vac line--if fuel leaks out, the FPR is bad. I checked that and didn't see any fuel.

No codes.

When I drove it today, it started fine twice. The third time, it started fine, then started to run rough. As I opened the door to get out and unplug the MAF, it smoothed out to normal again.

I was leaning toward fuel pressure or injectors, but now I'm leaning toward the MAF. When I was at the parts store getting a pressure tester, they had a record of the MAF I bought in 2008. Sucks that these things break so often (if that's what it is).

K87ZZ4

Thanks, all, for the help.

I just cleaned the MAF with some intake cleaner. I figure that's not a bad thing to do (I've had trouble with a dirty MAF on my GMC truck for years (reportedly) because of the K&N filter). If it starts running rough again, I hope to be able to unplug the MAF and see if that makes a difference.

I bought a fuel pressure tester (made by Innova, I think). I'm not sure about the quality. Is there an obvious better choice (before I open the package)?

Thanks!

summerst

Have the injectors ever been replaced? They should ohm at around 14.

K87ZZ4

I've been out of town for a while, but when I cranked it over tonight, it wouldn't start at all (it's been sitting for almost a week). It cranked for about 10 secs and nothing. I unplugged the MAF and I tried again and it started and immediately died. I tried again and it just cranked and cranked.

I got the pressure tester out later and it read 41 PSI when I turned the key to 'on' (I was kind of surprised). So, I started it and it fired right up, but then the pressure dropped to 10 PSI over the next 5-10 secs and it died. Again, when I turned the key to 'on', it read 41 PSI. It started up again and the pressure slowly dropped to 10 and it died.

When I turned the key to 'on' again, the pressure didn't budge (and I didn't hear the pump come on, either).

So, now I'm thinking fuel pump. Is it typical that a fuel pump will work intermittently before it dies? For some reason, I thought that they usually just gave up the ghost and quit working entirely.

I've read other posts that say replacing the fuel pump is pretty easy from the fuel filler door. Is that true for an 87?

ex-x-fire

Check for a fuel leak at the pressure regulator.
Your leak might be inside the tank, the rubber hose between the pump & the pipe that goes through the sending unit.

joe paco

does sound like pump since it starts and runs before losing pressure. leaking injectors or regulator would flood engine.

easy to pull thru the door. careful with the paper gasket under the cover. only goes back on one way also, notch to the right top I believe. as ex fre said, may be inside tank, not pump itself, but...you didn't hear pump prime, which sounds like pump, correct?

K87ZZ4

Right, the pump came on and primed a couple of times, but then didn't come on after that, even though the pressure gauge read only 10 PSI.

It's the intermittent part of it that's making it tough. Sometimes the pump comes on and pressure is spot on, sometimes the pump doesn't come on.

And then we have the pressure dropping, but only when running.

I *believe* I did that by pulling the vacuum hose off the regulator when the system is under pressure. If it were leaking, I would see fuel come out the vacuum connection, right?

K87ZZ4

Oh, and the fuel filter was replaced about 15,000 miles ago.

joe paco

I think the prime is not key on-off-onoff-on off. after the first couple, key has to be off for about 10 secs.

if it only loses pressure running, it is injectors, regulator, pump, not in any order. can unhook reg vac line, look for a reaction. prob not injectors IF it runs ok.

K87ZZ4

Ahhhh... I guess that makes sense, thanks Joe.

I tried it a couple of times today. This morning, at key on, the pump came on and primed up to 41 PSI, then started slowly dropping, but it started and came back up to 41 once it was running. After about 15 secs, it dropped to 35 PSI, but still ran smooth.

I unplugged the regulator and it primed, started dropping, but started again and ran smoothly at 45 PSI.

Tonight, it primed up to 41 at key on, started up fine and then slowly died over 5-10 secs as the pressure dropped to 10 PSI. The pump then came back on it went back up to 41. It started again, and ran smooth for a couple seconds, then slowly died again as the pressure dropped.

So, it seems to work good enough when it decides to work and loses pressure when it decides NOT to work.

So, sounds like it could be what ex-x-fire mentioned (leak inside the tank). Could also be a pump just going bad? Or do they not behave this way when they die?

If I'm going to the trouble to pull the fuel pump out to check and maybe fix the hose between the pump and the sending unit, should I just replace the pump? And the filter sock?

Anything else I should replace/do while I'm at it?

I wouldn't be surprised if the fuel pump is original (I've had the car for 15 years and haven't replaced it).

As always, thanks much for the help!

AGENT 86

Put a meter on the fuel pump fuse and check to see if there is still 12v heading to pump, as pressure drops to 10 psi.
If it is, your pump may be on it's last leg, if it isn't, start looking at your pump relay and oil pressure switch.

FostersPerformance

Fuel pressure when key is first turned on, should jump up, stay there a few seconds, then drop a little before it settles. They are 'suppossed' to hold that pressure indefinatly, but none do.
If you think injectors are leaking, get in car and put the throttle to WOT for a minute. Then try to start. If it fires up, you have leaking injectors.

I work on boats and do this alot. Get a fuel injector repair harness from napa or whoever sells a replacement fuel injector end. Take a 9 volt battery and go one by one to each injector with your harness. Repeatly and momentarily touch the 2 wires to the battery. You should be able to hear and feel them opening and closing. Polarity shouldnt matter, just touch the battery quickly and momentarily.

If you have a stuck one it should be obvious.

Another way is to have someone keep cyclying the key on and off to keep a set fuel pressure in the gauge. Unplug each injector one by one untill the leak down on the gauge stops.

If they stick by a quality fuel system cleaner. Open it and smell it. If it smells like ammonia, thats the good stuff. Run it and beat on the motor a bit, espically low rpm, heavy load operation. Most free up.

Good luck

leesvet

In this fuel system there are only a couple possible things that prevent the pump from running...intermittent running narrows it a bit.

Fuel relay,, will do the off/on thing BUT when the engine is already running, the relay is insignificant and meaningless BECAUSE the power comes thru the OIL pressure SWITCH to operate the fuel pump...so the relay can be in Libya and the engine still runs...

The Pump itself...what we overlook is the fact that whenever we see a plugged up fuel filter, all that crap went thru the pump to get there. That does its damage to the rubber impeller and soft parts. They eventually bind with damaged rotating parts and the low power motor just does not have the ability to make it turn. Thats so a struggling motor does not get too hot for obvious reasons.....althought these DO get warm and are designed to be submerged in fuel to keep cool..another reason to never drive around with less than 1/4 tank gas.

Try turning the key ON and watching the pressure. It should show a bump as the key is turned to ON. Turn it OFF....WAIT 10 seconds as Joe suggested....now turn ON again. Should be another bump. Turning the key ON too soon will not get the pump to run. The ECM waits so it does not flood the engine.
IF you are getting the pump to run ok this way, go back to the filter AND the pump strainer.
The pick-up tube or pulsator don;t come apart and then work later. Its apart and will stay that way until someone puts it back together in the tank assy. Anytime you repair the intank hoses be certain to use fuel inj hose thats made to be submerged in fuel. There IS a difference.

Whats I highly advise to everyone with similar issues and those that ARE going in the tank, is to buy a new pump, tank gasket (rubber) a few new small hose clamps, a new pump sock/strainer and a new fuel filter.
Run the tank down as far as possible before pulling the pump out. Look in to see if there is alot of trash. If so, siphon what you can and wipe the rest with clean rags. Use CAUTION>>> the fume will collect and get thick....keep a fan on the general area to disperse any fumes in the work area..

When you repair with a new pump, strainer and filter you start fresh. A new relay doesn;t hurt since its only another $7.
DO run the system dry and/or to zero pressure before d/c the filter lines. it WILL siphon too. D/C the hoses at the pump before the filter and you wear less of the fuel.

Learn the normal behavior of the gauge. When you key ON you see it jump to 40+ and stay. As soon as the eng starts it drops to 38 or 35...thats ok. The needle shows you that fuel is being used and the 35 psi shows that is what the pump/regulator is able to keep up with under that condition. Thats where the pressure is "set". Many folks use adjustable regulators so they can dial it up to meet demands of performance built engines.
As rpm rises the needle will try to drop but recovers as the regulator adjust to the demand and lets more fuel to the rails.
That test gauge will tell you almosty everything you need to know to diagnose fuel related problems. You can see the inj operating thru the gauge, and learn things about the engine as well.


This is important...
during cranking you can see the needle flicker as the engine rotates before it fires and runs. This is showing you that the stored fuel pressure is dropping from the injectors cycling and letting small shots of fuel in with each crankshaft rotation. This tells you that the injectors ARE working and doing what they should be. As the engine fires and runs, the distributer sends its signal the the ECM that OK's the injectors to continue to operate since the engine IS running and able to use the fuel being sent. Seeing the gauge needle flick and drop as the starter turns is a good easy way to know that the inj are cycling and operating as a system. Individual inj can still have issues, but the system is operating if its using that fuel thats been sent in the 2 seconds prime.

K87ZZ4

Thanks for the tip on checking voltage to the relay.

I put a test light on the Fuel Relay fuse and it comes on for 2 secs when I turn the key to on, but the pump doesn't come on and the pressure doesn't move at all.

BTW, I found the diagram of the fuel pump relay in the FSM, but it doesn't say where, on the car, it is.

Twice today, the pump is not coming on at all when I turn the key to ON.

K87ZZ4

So I figure it is either the relay or the pump, at this point (since the pump won't come on at all). I don't know where the relay is, so I started trying to get the pump out. It's probably 25 years old, so I'm sure it's not a bad idea to replace it.

I managed to get the return line hose loose, but I can't get the supply line hose loose. I'm afraid to be too rough with it with a pair of pliers because the hose is 25 years old. I'm sure it should be replaced, too (but it looks like I would have to replace the whole fuel line to do it). Any suggestions for removing a 25-year-old fuel hose without ruining it? There's not a lot of space to work, either. And that hose is covering the last of the 10 mm bolts that hold the assembly in the tank.

AGENT 86

Just inward of booster on firewall.



If you apply 12v to terminal "G" on the ALDL connector, the pump should be powered until power from "G" is removed.
This can help with testing.