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.

2. 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.

3. 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.

 

[snip]

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.

 

Hmmm... interesting observation. This just reminded me that around the
time the car started acting up, we could hear a whistling sound after
first starting the car and at idle. The sound seemed to be coming from
the under passenger side, though we never could figure out from where
exactly. I'll get on Google and see if I can figure out how to check
etc. Thanks!

 

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.

 

is it possible that you have water in your gas????

 

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.

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

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

4. 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.

 

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?

 

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.

 

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.

 

<<snip>>

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.

 

Thanks, but you must have missed the initial post:

 

Neil Nelson wrote:

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).

 

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
one only lasted 6 months. No doubt because I let all that debris fall into
the tank. I also bought just the pump and not the assembly. You have to
figure out how to put it all together, but if you pay attention, it's not
hard.