1988 Caravan 3.0 won't start

Symptoms (in order):

  1. Freeway operation was fine, then the car would stumble & start to stall when coming off the freeway & stopping at the first light -- had to keep foot on the gas & brake to keep the revs up. Then similar stalling at low speed (0-15 mph) and when accelerating to change lanes or enter the freeway.

  1. The car then began to have problems starting -- turn the key and the engine would crank but not start, turn the key off and on and the car would usually start on the 2nd or 3rd try. (battery ok, distrib cap, wires, plugs replaced approx 1,500 miles ago). But just after starting & while still in park the engine would on occasion race or stumble, or both -- different symptoms on different starts.

  2. Car finally stalled out at freeway speed & had to be towed home. Refuses to start since.

- The car will crank fine but not start

- No error code (other than 55 end-of-codes)

- Fuel filter is clean and working (removed & inspected)

- Car will start immediately if TB/Carb cleaner is sprayed into the throttle body - but will only run while the TB/Carb cleaner is present in the TB. When started w/cleaner the engine sounds strong & smooth - so it doesn't appear to be distrib, wires, rotor etc.

- When turning the key, the fuel pump whirs for 1-2 sec (as normal) & fuel pressure builds up (don't have a fuel pressure gauge but fuel is definitely getting up into the fuel line in the engine compartment and to the fuel regulator (see below)

- Fuel is making it up to the engine compartment - I took off the rubber hoses from the fuel lines in the engine compartment to test, cranked the engine and fuel is pumping just fine, return line is dry.

- Removed throttle body & cleaned thoroughly and as far into the plenum as I could without removing the plenum - no change in starting after.

Neighbor said it's the fuel pump (his guess) but given that the pump does whir & push fuel up into the engine compartment line I'm hoping that the pump is working ok. I also tend to think that because of this (getting fuel up into the line) that the car would at least fire on it's own, and then possibly die out if the fuel pump pressure wasn't sufficient. Again, the car starts immediately when TB/Carb cleaner is sprayed into the TB, and as long as there is sufficient fuel from the cleaner in the TB the engine revs strong & sounds smooth.

I've read all sorts of posts for this engine regarding MAP sensors, HALL effect plates, fuel rail/injectors, O2 sensors, TPI sensors, PVC, etc., but before I start shotgunning these sort of things, or just jumping in and replacing a fuel pump, I'd appreciate any advise on what logically I should check next and in what order.

Reply to
glgxg
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Test the injector(s) circuit too see whether they are being switched. A simple 12 volt test light across the injector connectors will be sufficient.

Measure the fuel pressure, don't guess at it. Since there are no exotic fuel line fittings on this vehicle, a gauge set-up should be cheap and simple to devise.

The 3.0 doesn't use any Hall Effect devices for engine management, so don't let anyone sell you one...

However, the distributor -does- contain a dual optical trigger, not considered to be failure prone but they do fail on occasion. The fact that your vehicle is supplying spark in that it runs on carb cleaner negates the likelyhood that the optical triggers have failed.

The MAP, TPS etc, are all testable with a DVOM, no need to throw parts at it.

Reply to
Neil Nelson

i donot think your problem is the fuel pump. If the fuel pump is borken, it does not pump fuel at all. There might be soem cases where the presure of the pump is not enought but i donot know how to diagnotic it.

it might be a good idea to check if there is a blown fuse that can control the injection system. I donot know how to test if your injectors are workign or if they get signal to spray fuel. (i'm totally blank about the electrical injection system.) my guess is that your injection system does not let the gas in to the engine.

good luck.

Reply to
ulas cosar coskun

Reply to
mic canic

Apologies to all -- I don't mean to be a "hit & run" poster - I've just not much of a chance to work on the car since my last post.

Since my last post I've done the following:

  1. Check the Throttle Position Sensor (TPS) with an ohm meter (one lead to the center TPS connector, the other to other two connections - the TPS readings show constant and smooth reading on both tests.

  1. Checked the vacuum hoses (visually) and can find no obvious problems. I paid particular attention to the MAP sensor hose etc.

  2. Disconnected the MAP sensor and tried to start - no change.

  1. Re-fired the car by spraying TBS/Carburetor cleaner into the throttle body - the car will start and both idle and rev using the gas pedal as long as there is cleaner in the throttle body/plenum.

I've not yet measured the fuel or vacuum pressure (I do know that fuel is getting to the engine compartment via the fuel pump, but don't think that the fuel injectors are firing at all). Reason is that the local auto store charges $50 for a fuel gauge and $30 for a vacuum gauge -- for $80 I can get the car towed three blocks with change left over.

Neil mentioned testing the injecter circuit - I suppose that there is a proper way to do this, so it's off to the book store tomorrow to see if I can find a repair manual. My guess is that something is definitely wrong with the fuel injectors -- they are not being turned on for some reason. My reasoning for this is that there is indeed fuel getting through the filter up into the hose into the engine compartment -- the fuel pump is working, and even if I only had a few pounds of pressure in the line the care should at least attempt to start, but does not.

Oddly enough, I was taking my wife to work the other morning in our other car and what should pull up beside me but a 1988 Caravan LE -- exact same paint job and interior colors except this one looked like it was brand new -- nearly the exact same car but this one didn't make a sound at idle and purred quietly away from the light just like new. Obviously the owner of that car knew the difference between a TPS and an ECM :-)

Anyway - I'd be sure to update and let you folks know if I get this car running again and how.

G.

And in response to mic canic: no there isn't any possibility that there is water in my gas - I've disconnected the line in the engine compartment, allowed the pump to push gas into a glass container and have seen no sign of contamination in the fuel at all. Thanks for asking though.

mic canic wrote:

Reply to
glgxg

Or, you could get an oil pressure gauge, a 5/16" plastic vacuum tee, some fuel line, some #6 hose clamps and build your own fuel pressure gauge. You'll have to disconnect the feed hose where it crosses over to the engine to Tee it in, but you'd have to do that with a store bought dedicated gauge anyway.

All you need is a common garden variety 12 volt test light, which should be part of your tool kit anyway. Disconnect an injector, connect the test light between the two connector terminals, have someone crank the engine and watch for the light to flash (it should).

Since you went that far, when you were pumping gasoline into the jar, did it come out under pressure at a rather visious rate, or did it more or less flow out?

Reply to
Neil Nelson

For $28 I got a Chilton's repair book, T connector, 6/12V test light, and a Monkey Grip SUV/RV tire guage (it has a decent dial & 4 inch hose coming off of it and measures up to 80 psi). The $12 oil pressure guage that I looked at had a poorly marked dial & the next cheaper was $20 something dollars - I'll wack the metal fitting off the SUV/RV pressure guage and T into it's hose. I already had fuel hose (both intake and return) and clamps from when I replaced the cracked & leaking hoses 2 months ago.

I plan to spend the rest of the day reading the repair book and familiarize myself with all the part locations etc., & making the pressure guage, and then will set out to see what I can figure out this Sunday & Monday... there must be a reason they call this labor day weekend :-)

Unfortunately I was alone when I did this, so I didn't actually see the flow -- I just hooked it up to the glass jar & then switched the fuel pump on by turning the key to the on position. I'll get my son to help me this time and will check before I hook up the the guage.

Thanks for all your advise & I'll report back in a day or two.

Reply to
glgxg

Very inventive, my compliments.

I'll gladly trade you the Muncie M-20 transmission I'm rebuilding. Seems this transmission has spent the last 30 or so years with STP as the lubricant, stubborn black goo coating everything inside.

Hell, just hook up the gauge.

My pleasure.

Reply to
Neil Nelson

Just jumping in here...

Have you checked to insure that the timing belt has not failed? Crank the engine with the distributor cap off and see if it is turning.

Reply to
noone

Thanks, but you must have missed the initial post:

body - but will only run while the TB/Carb cleaner is present in the TB. When started w/cleaner the engine sounds strong & smooth - so it doesn't appear to be distrib, wires, rotor etc.

Reply to
glgxg

Here is today's update:

Well it appears that the fuel pump is probably bad after all. I hooked up the fuel pressure gauge at the engine and the pressure only read about 4 psi by just turning on the fuel pump, and 6-7 psi with cranking

-- nowhere near the 45-50 psi it should be. I was a still a little skeptical at first and thought perhaps the gauge that I put together might not be working so well, so I disconnected the gauge and watched while my son cranked the car.... got gas, but it barely spurted out of the line (more like a dribble).

Next we removed the fuel filter and T'ed into the line between the filter and the gas tank - same readings.

It looks as if we'll go and buy a new fuel pump & a new filter (just because). The neighbor who correctly diagnosed the pump in the first place said he'd give me discount if I bought my own part and had the car towed to his shop... for a mere $240 in labor he'll put the pump in for me... right. I've instructions from on how to do the removal & installation from usenet & the book, plus a strapping strong teenager to help. So other than the obviously grungy job of removing a 16 year old tank etc., I think we can do this on our own.

The good news is that we've learned something in the process & we now have a pretty cool, almost home-made fuel pressure gauge :-) I obviously haven't calibrated or checked the gauge against a professional one, but I'm pretty confident that the gauge is working just fine.

Now the question is what pump to buy (on a very limited budget for a car this old):

Kragen have Master E7074H pump & assembly for $119.99 and just the pump itself (Master E7012) for $84.99. I figure that while I have everything apart that I should probably go for the E7074H as it includes the pump and pump assy. They also have Carter pumps & assy that are a bit higher than what I care to spend for a car this old (Carter P74501H pump & assy for $177.99 & Carter P74083 pump for $145.99).

Reply to
glgxg

I did this job on my '88 recently. Here's a few tips:

There's a vent tube that goes from the top of the tank to near the top of the fuel filler tube. It's fairly rigid and will crack or break if you're not careful. This tube is what makes the gas station's auto shut off work on their pumps (works by pressure differential). A crack will do it in and you won't get a pint of fuel in the tank before it will shut off :-(

I did this job twice. The first time it was in a parking lot (ugghhhh!!!) and I just lowered the tank and worked underneath. Even so, I think this is where I damaged the vent tube. This method worked quite well.

The second time, I removed the entire tank (I had to repair the vent tube). This was quite unpleasant for a first time DIY. The vent tube is no longer available, so I had to juryrig using coolant hose and elbow. Also, it's just a pain to remove the tank all the way. It wasn't the hardest thing I've done, but it's still a pain.

VERY IMPORTANT: Clean the top of the tank where the fuel pump is removed. You DO NOT want dust and debris falling into the tank. Use a vacuum cleaner, brush, compressed air, brake cleaner, a combination of these, whatever will to the job.

Replace the fuel filter whenever you replace the fuel pump.

I'm glad I bought the lifetime warranty pump (from NAPA) because the first >

Reply to
David Allen

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